Objective-C编码规范：26个方面解决iOS开发问题

背景

这里有些关于编码风格Apple官方文档，如果有些东西没有提及，可以在以下文档来查找更多细节：

The Objective-C Programming Language ：

https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/ProgrammingWithObjectiveC/Introduction/Introduction.html

Cocoa Fundamentals Guide ：

https://developer.apple.com/legacy/library/documentation/Cocoa/Conceptual/CocoaFundamentals/Introduction/Introduction.html

Coding Guidelines for Cocoa ：

https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/CodingGuidelines/CodingGuidelines.html

iOS App Programming Guide：

https://developer.apple.com/library/ios/#documentation/iphone/conceptual/iphoneosprogrammingguide/Introduction/Introduction.html

语言

应该使用US英语。

应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="typ" style="color: rgb(102, 0, 102);">UIColor</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">myColor </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">[</span><span class="typ" style="color: rgb(102, 0, 102);">UIColor</span><span class="pln" style="color: rgb(0, 0, 0);"> whiteColor</span><span class="pun" style="color: rgb(102, 102, 0);">];</span><span class="pln" style="color: rgb(0, 0, 0);"> </span></code>

不应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="typ" style="color: rgb(102, 0, 102);">UIColor</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">myColour </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">[</span><span class="typ" style="color: rgb(102, 0, 102);">UIColor</span><span class="pln" style="color: rgb(0, 0, 0);"> whiteColor</span><span class="pun" style="color: rgb(102, 102, 0);">];</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

代码组织

在函数分组和

protocol

/

delegate

实现中使用

#pragma
mark -

来分类方法，要遵循以下一般结构：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="com" style="color: rgb(136, 0, 0);">#pragma</span><span class="pln" style="color: rgb(0, 0, 0);"> mark </span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">Lifecycle</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">instancetype</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">init </span><span class="pun" style="color: rgb(102, 102, 0);">{}</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="kwd" style="color: rgb(0, 0, 136);">void</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">dealloc </span><span class="pun" style="color: rgb(102, 102, 0);">{}</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="kwd" style="color: rgb(0, 0, 136);">void</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">viewDidLoad </span><span class="pun" style="color: rgb(102, 102, 0);">{}</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="kwd" style="color: rgb(0, 0, 136);">void</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">viewWillAppear</span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="pln" style="color: rgb(0, 0, 0);">BOOL</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">animated </span><span class="pun" style="color: rgb(102, 102, 0);">{}</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="kwd" style="color: rgb(0, 0, 136);">void</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">didReceiveMemoryWarning </span><span class="pun" style="color: rgb(102, 102, 0);">{}</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">#pragma</span><span class="pln" style="color: rgb(0, 0, 0);"> mark </span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">Custom</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">Accessors</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="kwd" style="color: rgb(0, 0, 136);">void</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">setCustomProperty</span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="pln" style="color: rgb(0, 0, 0);">id</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">value </span><span class="pun" style="color: rgb(102, 102, 0);">{}</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">id</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">customProperty </span><span class="pun" style="color: rgb(102, 102, 0);">{}</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">#pragma</span><span class="pln" style="color: rgb(0, 0, 0);"> mark </span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">IBActions</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="typ" style="color: rgb(102, 0, 102);">IBAction</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">submitData</span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="pln" style="color: rgb(0, 0, 0);">id</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">sender </span><span class="pun" style="color: rgb(102, 102, 0);">{}</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">#pragma</span><span class="pln" style="color: rgb(0, 0, 0);"> mark </span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">Public</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="kwd" style="color: rgb(0, 0, 136);">void</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">publicMethod </span><span class="pun" style="color: rgb(102, 102, 0);">{}</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">#pragma</span><span class="pln" style="color: rgb(0, 0, 0);"> mark </span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">Private</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="kwd" style="color: rgb(0, 0, 136);">void</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">privateMethod </span><span class="pun" style="color: rgb(102, 102, 0);">{}</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">#pragma</span><span class="pln" style="color: rgb(0, 0, 0);"> mark </span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">Protocol</span><span class="pln" style="color: rgb(0, 0, 0);"> conformance
</span><span class="com" style="color: rgb(136, 0, 0);">#pragma</span><span class="pln" style="color: rgb(0, 0, 0);"> mark </span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">UITextFieldDelegate</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">#pragma</span><span class="pln" style="color: rgb(0, 0, 0);"> mark </span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">UITableViewDataSource</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">#pragma</span><span class="pln" style="color: rgb(0, 0, 0);"> mark </span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">UITableViewDelegate</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">#pragma</span><span class="pln" style="color: rgb(0, 0, 0);"> mark </span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">NSCopying</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">id</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">copyWithZone</span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="typ" style="color: rgb(102, 0, 102);">NSZone</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*)</span><span class="pln" style="color: rgb(0, 0, 0);">zone </span><span class="pun" style="color: rgb(102, 102, 0);">{}</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">#pragma</span><span class="pln" style="color: rgb(0, 0, 0);"> mark </span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">NSObject</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="typ" style="color: rgb(102, 0, 102);">NSString</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*)</span><span class="pln" style="color: rgb(0, 0, 0);">description </span><span class="pun" style="color: rgb(102, 102, 0);">{}</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

空格

缩进使用4个空格，确保在Xcode偏好设置来设置。（raywenderlich.com使用2个空格）
方法大括号和其他大括号(if/else/switch/while 等.)总是在同一行语句打开但在新行中关闭。

应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="kwd" style="color: rgb(0, 0, 136);">if</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">user</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">isHappy</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">//Do something  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="kwd" style="color: rgb(0, 0, 136);">else</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">//Do something else  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

不应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="kwd" style="color: rgb(0, 0, 136);">if</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">user</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">isHappy</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">//Do something  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">else</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">//Do something else  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

在方法之间应该有且只有一行，这样有利于在视觉上更清晰和更易于组织。在方法内的空白应该分离功能，但通常都抽离出来成为一个新方法。
优先使用

auto-synthesis

。但如果有必要，@synthesize和@dynamic应该在实现中每个都声明新的一行。
应该避免以冒号对齐的方式来调用方法。因为有时方法签名可能有3个以上的冒号和冒号对齐会使代码更加易读。请不要这样做，尽管冒号对齐的方法包含代码块，因为Xcode的对齐方式令它难以辨认。

应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="com" style="color: rgb(136, 0, 0);">// blocks are easily readable  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">[</span><span class="typ" style="color: rgb(102, 0, 102);">UIView</span><span class="pln" style="color: rgb(0, 0, 0);"> animateWithDuration</span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="lit" style="color: rgb(0, 102, 102);">1.0</span><span class="pln" style="color: rgb(0, 0, 0);"> animations</span><span class="pun" style="color: rgb(102, 102, 0);">:^{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">// something  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span><span class="pln" style="color: rgb(0, 0, 0);"> completion</span><span class="pun" style="color: rgb(102, 102, 0);">:^(</span><span class="pln" style="color: rgb(0, 0, 0);">BOOL finished</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">// something  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}];</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

不应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="com" style="color: rgb(136, 0, 0);">// colon-aligning makes the block indentation hard to read  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">[</span><span class="typ" style="color: rgb(102, 0, 102);">UIView</span><span class="pln" style="color: rgb(0, 0, 0);"> animateWithDuration</span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="lit" style="color: rgb(0, 102, 102);">1.0</span><span class="pln" style="color: rgb(0, 0, 0);">
animations</span><span class="pun" style="color: rgb(102, 102, 0);">:^{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">// something  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span><span class="pln" style="color: rgb(0, 0, 0);">
completion</span><span class="pun" style="color: rgb(102, 102, 0);">:^(</span><span class="pln" style="color: rgb(0, 0, 0);">BOOL finished</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">// something  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}];</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

注释

当需要注释时，注释应该用来解释这段特殊代码为什么要这样做。任何被使用的注释都必须保持最新或被删除。

一般都避免使用块注释，因为代码尽可能做到自解释，只有当断断续续或几行代码时才需要注释。例外：这不应用在生成文档的注释。

命名

Apple命名规则尽可能坚持，特别是与这些相关的memory management rules (NARC)。

长的，描述性的方法和变量命名是好的。

应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="typ" style="color: rgb(102, 0, 102);">UIButton</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">settingsButton</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

不应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="typ" style="color: rgb(102, 0, 102);">UIButton</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">setBut</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

三个字符前缀应该经常用在类和常量命名，但在Core Data的实体名中应被忽略。对于官方的raywenderlich.com书、初学者工具包或教程，前缀

RWT

应该被使用。

常量应该使用驼峰式命名规则，所有的单词首字母大写和加上与类名有关的前缀。

应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="kwd" style="color: rgb(0, 0, 136);">static</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">NSTimeInterval</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="kwd" style="color: rgb(0, 0, 136);">const</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">RWTTutorialViewControllerNavigationFadeAnimationDuration</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">0.3</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

不应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="kwd" style="color: rgb(0, 0, 136);">static</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">NSTimeInterval</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="kwd" style="color: rgb(0, 0, 136);">const</span><span class="pln" style="color: rgb(0, 0, 0);"> fadetime </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">1.7</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);"> </span></code>

属性也是使用驼峰式，但首单词的首字母小写。对属性使用

auto-synthesis

，而不是手动编写@synthesize语句，除非你有一个好的理由。

应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="lit" style="color: rgb(0, 102, 102);">@property</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">strong</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> nonatomic</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">NSString</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">descriptiveVariableName</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

不应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="pln" style="color: rgb(0, 0, 0);">id varnm</span><span class="pun" style="color: rgb(102, 102, 0);">;</span></code>

下划线

当使用属性时，实例变量应该使用

self.

来访问和改变。这就意味着所有属性将会视觉效果不同，因为它们前面都有

self.

。

但有一个特例：在初始化方法里，实例变量(例如，

_variableName

)应该直接被使用来避免

getters

/

setters

潜在的副作用。

局部变量不应该包含下划线。

方法

在方法签名中，应该在方法类型(-/+ 符号)之后有一个空格。在方法各个段之间应该也有一个空格(符合Apple的风格)。在参数之前应该包含一个具有描述性的关键字来描述参数。

“

and

”这个词的用法应该保留。它不应该用于多个参数来说明，就像

initWithWidth:height

以下这个例子：

应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="kwd" style="color: rgb(0, 0, 136);">void</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">setExampleText</span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="typ" style="color: rgb(102, 0, 102);">NSString</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*)</span><span class="pln" style="color: rgb(0, 0, 0);">text image</span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="typ" style="color: rgb(102, 0, 102);">UIImage</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*)</span><span class="pln" style="color: rgb(0, 0, 0);">image</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="kwd" style="color: rgb(0, 0, 136);">void</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">sendAction</span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="pln" style="color: rgb(0, 0, 0);">SEL</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">aSelector to</span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="pln" style="color: rgb(0, 0, 0);">id</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">anObject forAllCells</span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="pln" style="color: rgb(0, 0, 0);">BOOL</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">flag</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">id</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">viewWithTag</span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="typ" style="color: rgb(102, 0, 102);">NSInteger</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">tag</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">instancetype</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">initWithWidth</span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="typ" style="color: rgb(102, 0, 102);">CGFloat</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">width height</span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="typ" style="color: rgb(102, 0, 102);">CGFloat</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">height</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);"> </span></code>

不应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="kwd" style="color: rgb(0, 0, 136);">void</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">setT</span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="typ" style="color: rgb(102, 0, 102);">NSString</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*)</span><span class="pln" style="color: rgb(0, 0, 0);">text i</span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="typ" style="color: rgb(102, 0, 102);">UIImage</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*)</span><span class="pln" style="color: rgb(0, 0, 0);">image</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="kwd" style="color: rgb(0, 0, 136);">void</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">sendAction</span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="pln" style="color: rgb(0, 0, 0);">SEL</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">aSelector </span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="pln" style="color: rgb(0, 0, 0);">id</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">anObject </span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="pln" style="color: rgb(0, 0, 0);">BOOL</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">flag</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">id</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">taggedView</span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="typ" style="color: rgb(102, 0, 102);">NSInteger</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">tag</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">instancetype</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">initWithWidth</span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="typ" style="color: rgb(102, 0, 102);">CGFloat</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">width andHeight</span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="typ" style="color: rgb(102, 0, 102);">CGFloat</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">height</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">instancetype</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">initWith</span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="kwd" style="color: rgb(0, 0, 136);">int</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">width </span><span class="kwd" style="color: rgb(0, 0, 136);">and</span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="kwd" style="color: rgb(0, 0, 136);">int</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">height</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">  </span><span class="com" style="color: rgb(136, 0, 0);">// Never do this.  </span></code>

变量

变量尽量以描述性的方式来命名。单个字符的变量命名应该尽量避免，除了在

for()

循环。

星号表示变量是指针。例如：

NSString *text

既不是 NSString* text

也不是 NSString * text，除了一些特殊情况下常量。

私有变量应该尽可能代替实例变量的使用。尽管使用实例变量是一种有效的方式，但更偏向于使用属性来保持代码一致性。

通过使用’

back

’属性(

_variable

，变量名前面有下划线)直接访问实例变量应该尽量避免，除了在初始化方法

(init,

initWithCoder:

,
等…)，

dealloc

方法和自定义的

setters

和

getters

。想了解关于如何在初始化方法和

dealloc

直接使用

Accessor

方法的更多信息，查看这里。

应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="lit" style="color: rgb(0, 102, 102);">@interface</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">RWTTutorial</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">NSObject</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="lit" style="color: rgb(0, 102, 102);">@property</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">strong</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> nonatomic</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">NSString</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">tutorialName</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="lit" style="color: rgb(0, 102, 102);">@end</span></code>

不应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="lit" style="color: rgb(0, 102, 102);">@interface</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">RWTTutorial</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">NSObject</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">NSString</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">tutorialName</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

属性特性

所有属性特性应该显式地列出来，有助于新手阅读代码。属性特性的顺序应该是storage、atomicity，与在Interface Builder连接UI元素时自动生成代码一致。

应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="lit" style="color: rgb(0, 102, 102);">@property</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">weak</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> nonatomic</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">IBOutlet</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">UIView</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">containerView</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="lit" style="color: rgb(0, 102, 102);">@property</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">strong</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> nonatomic</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">NSString</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">tutorialName</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

不应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="lit" style="color: rgb(0, 102, 102);">@property</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">nonatomic</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> weak</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">IBOutlet</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">UIView</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">containerView</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="lit" style="color: rgb(0, 102, 102);">@property</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">nonatomic</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">NSString</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">tutorialName</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

NSString

应该使用

copy

而不是

strong

的属性特性。

为什么？即使你声明一个

NSString

的属性，有人可能传入一个

NSMutableString

的实例，然后在你没有注意的情况下修改它。

应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="lit" style="color: rgb(0, 102, 102);">@property</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">copy</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> nonatomic</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">NSString</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">tutorialName</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

不应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="lit" style="color: rgb(0, 102, 102);">@property</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">strong</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> nonatomic</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">NSString</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">tutorialName</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

点符号语法

点语法是一种很方便封装访问方法调用的方式。当你使用点语法时，通过使用

getter

或

setter

方法，属性仍然被访问或修改。想了解更多。

阅读:https://developer.apple.com/library/ios/documentation/cocoa/conceptual/ProgrammingWithObjectiveC/EncapsulatingData/EncapsulatingData.html

点语法应该总是被用来访问和修改属性，因为它使代码更加简洁。

[]

符号更偏向于用在其他例子。

应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="pln" style="color: rgb(0, 0, 0);">objc
</span><span class="typ" style="color: rgb(102, 0, 102);">NSInteger</span><span class="pln" style="color: rgb(0, 0, 0);"> arrayCount </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">[</span><span class="kwd" style="color: rgb(0, 0, 136);">self</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">array count</span><span class="pun" style="color: rgb(102, 102, 0);">];</span><span class="pln" style="color: rgb(0, 0, 0);">
view</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">backgroundColor </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">[</span><span class="typ" style="color: rgb(102, 0, 102);">UIColor</span><span class="pln" style="color: rgb(0, 0, 0);"> orangeColor</span><span class="pun" style="color: rgb(102, 102, 0);">];</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">[</span><span class="typ" style="color: rgb(102, 0, 102);">UIApplication</span><span class="pln" style="color: rgb(0, 0, 0);"> sharedApplication</span><span class="pun" style="color: rgb(102, 102, 0);">].</span><span class="kwd" style="color: rgb(0, 0, 136);">delegate</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

不应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="typ" style="color: rgb(102, 0, 102);">NSInteger</span><span class="pln" style="color: rgb(0, 0, 0);"> arrayCount </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="kwd" style="color: rgb(0, 0, 136);">self</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">array</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">count</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">[</span><span class="pln" style="color: rgb(0, 0, 0);">view setBackgroundColor</span><span class="pun" style="color: rgb(102, 102, 0);">:[</span><span class="typ" style="color: rgb(102, 0, 102);">UIColor</span><span class="pln" style="color: rgb(0, 0, 0);"> orangeColor</span><span class="pun" style="color: rgb(102, 102, 0);">]];</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">UIApplication</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">sharedApplication</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="kwd" style="color: rgb(0, 0, 136);">delegate</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

字面值

NSString

、

NSDictionary

、

NSArray

和

NSNumber

的字面值应该在创建这些类的不可变实例时被使用。请特别注意

nil

值不能传入

NSArray

和

NSDictionary

字面值，因为这样会导致crash。

应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="typ" style="color: rgb(102, 0, 102);">NSArray</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">names </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@[@</span><span class="str" style="color: rgb(0, 136, 0);">"Brian"</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"Matt"</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"Chris"</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"Alex"</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"Steve"</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"Paul"</span><span class="pun" style="color: rgb(102, 102, 0);">];</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">NSDictionary</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">productManagers </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@{@</span><span class="str" style="color: rgb(0, 136, 0);">"iPhone"</span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"Kate"</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"iPad"</span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"Kamal"</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"Mobile Web"</span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"Bill"</span><span class="pun" style="color: rgb(102, 102, 0);">};</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">NSNumber</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">shouldUseLiterals </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">@YES</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">NSNumber</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">buildingStreetNumber </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="lit" style="color: rgb(0, 102, 102);">10018</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

不应该:

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="typ" style="color: rgb(102, 0, 102);">NSArray</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">names </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">[</span><span class="typ" style="color: rgb(102, 0, 102);">NSArray</span><span class="pln" style="color: rgb(0, 0, 0);"> arrayWithObjects</span><span class="pun" style="color: rgb(102, 102, 0);">:@</span><span class="str" style="color: rgb(0, 136, 0);">"Brian"</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"Matt"</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"Chris"</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"Alex"</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"Steve"</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"Paul"</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="kwd" style="color: rgb(0, 0, 136);">nil</span><span class="pun" style="color: rgb(102, 102, 0);">];</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">NSDictionary</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">productManagers </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">[</span><span class="typ" style="color: rgb(102, 0, 102);">NSDictionary</span><span class="pln" style="color: rgb(0, 0, 0);"> dictionaryWithObjectsAndKeys</span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"Kate"</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"iPhone"</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"Kamal"</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"iPad"</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"Bill"</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"Mobile Web"</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="kwd" style="color: rgb(0, 0, 136);">nil</span><span class="pun" style="color: rgb(102, 102, 0);">];</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">NSNumber</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">shouldUseLiterals </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">[</span><span class="typ" style="color: rgb(102, 0, 102);">NSNumber</span><span class="pln" style="color: rgb(0, 0, 0);"> numberWithBool</span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);">YES</span><span class="pun" style="color: rgb(102, 102, 0);">];</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">NSNumber</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">buildingStreetNumber </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">[</span><span class="typ" style="color: rgb(102, 0, 102);">NSNumber</span><span class="pln" style="color: rgb(0, 0, 0);"> numberWithInteger</span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="lit" style="color: rgb(0, 102, 102);">10018</span><span class="pun" style="color: rgb(102, 102, 0);">];</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

常量

常量是容易重复被使用和无需通过查找和代替就能快速修改值。常量应该使用

static

来声明而不是使用

#define

，除非显式地使用宏。

应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="kwd" style="color: rgb(0, 0, 136);">static</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">NSString</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="kwd" style="color: rgb(0, 0, 136);">const</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">RWTAboutViewControllerCompanyName</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"RayWenderlich.com"</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">static</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">CGFloat</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="kwd" style="color: rgb(0, 0, 136);">const</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">RWTImageThumbnailHeight</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">50.0</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

不应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="com" style="color: rgb(136, 0, 0);">#define</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">CompanyName</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">@</span><span class="str" style="color: rgb(0, 136, 0);">"RayWenderlich.com"</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">#define</span><span class="pln" style="color: rgb(0, 0, 0);"> thumbnailHeight </span><span class="lit" style="color: rgb(0, 102, 102);">2</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

枚举类型

当使用enum时，推荐使用新的固定基本类型规格，因为它有更强的类型检查和代码补全。现在SDK有一个宏

NS_ENUM()

来帮助和鼓励你使用固定的基本类型。

例如：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="kwd" style="color: rgb(0, 0, 136);">typedef</span><span class="pln" style="color: rgb(0, 0, 0);"> NS_ENUM</span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="typ" style="color: rgb(102, 0, 102);">NSInteger</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">RWTLeftMenuTopItemType</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">RWTLeftMenuTopItemMain</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">RWTLeftMenuTopItemShows</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">RWTLeftMenuTopItemSchedule</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">};</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

你也可以显式地赋值(展示旧的

k-style

常量定义)：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="kwd" style="color: rgb(0, 0, 136);">typedef</span><span class="pln" style="color: rgb(0, 0, 0);"> NS_ENUM</span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="typ" style="color: rgb(102, 0, 102);">NSInteger</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">RWTGlobalConstants</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">RWTPinSizeMin</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">1</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">RWTPinSizeMax</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">5</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">RWTPinCountMin</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">100</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">RWTPinCountMax</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">500</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">};</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

旧的

k-style

常量定义应该避免除非编写Core Foundation C的代码。

不应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="kwd" style="color: rgb(0, 0, 136);">enum</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">GlobalConstants</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
kMaxPinSize </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">5</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);">
kMaxPinCount </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">500</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">};</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

Case语句

大括号在case语句中并不是必须的，除非编译器强制要求。当一个case语句包含多行代码时，大括号应该加上。

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="kwd" style="color: rgb(0, 0, 136);">switch</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">condition</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">case</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">1</span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">// ...  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">break</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">case</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">2</span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">// ...  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">// Multi-line example using braces  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">break</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">case</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">3</span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">// ...  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">break</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">default</span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">// ...  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">break</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

有很多次，当相同代码被多个cases使用时，一个

fall-through

应该被使用。一个f

all-through

就是在case最后移除’

break

’语句，这样就能够允许执行流程跳转到下一个case值。为了代码更加清晰，一个

fall-through

需要注释一下。

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="kwd" style="color: rgb(0, 0, 136);">switch</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">condition</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">case</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">1</span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">// ** fall-through! **  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">case</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">2</span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">// code executed for values 1 and 2  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">break</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">default</span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">// ...  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">break</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

当在switch使用枚举类型时，’

default

’是不需要的。例如：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="typ" style="color: rgb(102, 0, 102);">RWTLeftMenuTopItemType</span><span class="pln" style="color: rgb(0, 0, 0);"> menuType </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">RWTLeftMenuTopItemMain</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">switch</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">menuType</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">case</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">RWTLeftMenuTopItemMain</span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">// ...  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">break</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">case</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">RWTLeftMenuTopItemShows</span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">// ...  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">break</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">case</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">RWTLeftMenuTopItemSchedule</span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">// ...  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">break</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span><span class="pln" style="color: rgb(0, 0, 0);"> </span></code>

私有属性

私有属性应该在类的实现文件中的类扩展(匿名分类)中声明，命名分类(比如

RWTPrivate

或

private

)应该从不使用除非是扩展其他类。匿名分类应该通过使用

+Private.h

文件的命名规则暴露给测试。

例如：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="lit" style="color: rgb(0, 102, 102);">@interface</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">RWTDetailViewController</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">()</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="lit" style="color: rgb(0, 102, 102);">@property</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">strong</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> nonatomic</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">GADBannerView</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">googleAdView</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="lit" style="color: rgb(0, 102, 102);">@property</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">strong</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> nonatomic</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">ADBannerView</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">iAdView</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="lit" style="color: rgb(0, 102, 102);">@property</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">strong</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> nonatomic</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">UIWebView</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">adXWebView</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="lit" style="color: rgb(0, 102, 102);">@end</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

布尔值

Objective-C使用YES和NO。因为true和false应该只在CoreFoundation，C或C++代码使用。既然nil解析成NO，所以没有必要在条件语句比较。不要拿某样东西直接与YES比较，因为YES被定义为1和一个BOOL能被设置为8位。

这是为了在不同文件保持一致性和在视觉上更加简洁而考虑。

应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="kwd" style="color: rgb(0, 0, 136);">if</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">someObject</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{}</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">if</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(![</span><span class="pln" style="color: rgb(0, 0, 0);">anotherObject boolValue</span><span class="pun" style="color: rgb(102, 102, 0);">])</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{}</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

不应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="kwd" style="color: rgb(0, 0, 136);">if</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">someObject </span><span class="pun" style="color: rgb(102, 102, 0);">==</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="kwd" style="color: rgb(0, 0, 136);">nil</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{}</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">if</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">([</span><span class="pln" style="color: rgb(0, 0, 0);">anotherObject boolValue</span><span class="pun" style="color: rgb(102, 102, 0);">]</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">==</span><span class="pln" style="color: rgb(0, 0, 0);"> NO</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{}</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">if</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">isAwesome </span><span class="pun" style="color: rgb(102, 102, 0);">==</span><span class="pln" style="color: rgb(0, 0, 0);"> YES</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{}</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="com" style="color: rgb(136, 0, 0);">// Never do this.  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">if</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">isAwesome </span><span class="pun" style="color: rgb(102, 102, 0);">==</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="kwd" style="color: rgb(0, 0, 136);">true</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{}</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="com" style="color: rgb(136, 0, 0);">// Never do this.  </span></code>

如果

BOOL

属性的名字是一个形容词，属性就能忽略”

is

”前缀，但要指定get访问器的惯用名称。例如：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="lit" style="color: rgb(0, 102, 102);">@property</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">assign</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> getter</span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);">isEditable</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> BOOL editable</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

文字和例子从这里引用Cocoa Naming Guidelines。

条件语句

条件语句主体为了防止出错应该使用大括号包围，即使条件语句主体能够不用大括号编写(如，只用一行代码)。这些错误包括添加第二行代码和期望它成为if语句；还有，even more dangerous defect可能发生在if语句里面一行代码被注释了，然后下一行代码不知不觉地成为if语句的一部分。除此之外，这种风格与其他条件语句的风格保持一致，所以更加容易阅读。

应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="kwd" style="color: rgb(0, 0, 136);">if</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(!</span><span class="pln" style="color: rgb(0, 0, 0);">error</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">return</span><span class="pln" style="color: rgb(0, 0, 0);"> success</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

不应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="kwd" style="color: rgb(0, 0, 136);">if</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(!</span><span class="pln" style="color: rgb(0, 0, 0);">error</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">return</span><span class="pln" style="color: rgb(0, 0, 0);"> success</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

或

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="kwd" style="color: rgb(0, 0, 136);">if</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(!</span><span class="pln" style="color: rgb(0, 0, 0);">error</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="kwd" style="color: rgb(0, 0, 136);">return</span><span class="pln" style="color: rgb(0, 0, 0);"> success</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

三元操作符

当需要提高代码的清晰性和简洁性时，三元操作符?:才会使用。单个条件求值常常需要它。多个条件求值时，如果使用if语句或重构成实例变量时，代码会更加易读。一般来说，最好使用三元操作符是在根据条件来赋值的情况下。

Non-boolean

的变量与某东西比较，加上括号()会提高可读性。如果被比较的变量是

boolean

类型，那么就不需要括号。

应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="typ" style="color: rgb(102, 0, 102);">NSInteger</span><span class="pln" style="color: rgb(0, 0, 0);"> value </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">5</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
result </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">value </span><span class="pun" style="color: rgb(102, 102, 0);">!=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">0</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">?</span><span class="pln" style="color: rgb(0, 0, 0);"> x </span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);"> y</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
BOOL isHorizontal </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> YES</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
result </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> isHorizontal </span><span class="pun" style="color: rgb(102, 102, 0);">?</span><span class="pln" style="color: rgb(0, 0, 0);"> x </span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);"> y</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

不应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="pln" style="color: rgb(0, 0, 0);">result </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> a </span><span class="pun" style="color: rgb(102, 102, 0);">></span><span class="pln" style="color: rgb(0, 0, 0);"> b </span><span class="pun" style="color: rgb(102, 102, 0);">?</span><span class="pln" style="color: rgb(0, 0, 0);"> x </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> c </span><span class="pun" style="color: rgb(102, 102, 0);">></span><span class="pln" style="color: rgb(0, 0, 0);"> d </span><span class="pun" style="color: rgb(102, 102, 0);">?</span><span class="pln" style="color: rgb(0, 0, 0);"> c </span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);"> d </span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);"> y</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

Init方法

Init方法应该遵循Apple生成代码模板的命名规则，返回类型应该使用

instancetype

而不是

id

。

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">instancetype</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">init </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">self</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">[</span><span class="kwd" style="color: rgb(0, 0, 136);">super</span><span class="pln" style="color: rgb(0, 0, 0);"> init</span><span class="pun" style="color: rgb(102, 102, 0);">];</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">if</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="kwd" style="color: rgb(0, 0, 136);">self</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">// ...  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">return</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="kwd" style="color: rgb(0, 0, 136);">self</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

类构造方法

当类构造方法被使用时，它应该返回类型是

instancetype

而不是

id

。这样确保编译器正确地推断结果类型。

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="lit" style="color: rgb(0, 102, 102);">@interface</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">Airplane</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">+</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">instancetype</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">airplaneWithType</span><span class="pun" style="color: rgb(102, 102, 0);">:(</span><span class="typ" style="color: rgb(102, 0, 102);">RWTAirplaneType</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">type</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="lit" style="color: rgb(0, 102, 102);">@end</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

关于更多instancetype信息，请查看NSHipster.com。

CGRect函数

当访问CGRect里的

x

,

y

,

width

,
或

height

时，应该使用CGGeometry函数而不是直接通过结构体来访问。引用Apple的CGGeometry：

在这个参考文档中所有的函数，接受CGRect结构体作为输入，在计算它们结果时隐式地标准化这些rectangles。因此，你的应用程序应该避免直接访问和修改保存在CGRect数据结构中的数据。相反，使用这些函数来操纵rectangles和获取它们的特性。

应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="typ" style="color: rgb(102, 0, 102);">CGRect</span><span class="pln" style="color: rgb(0, 0, 0);"> frame </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="kwd" style="color: rgb(0, 0, 136);">self</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">view</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">frame</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">CGFloat</span><span class="pln" style="color: rgb(0, 0, 0);"> x </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">CGRectGetMinX</span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">frame</span><span class="pun" style="color: rgb(102, 102, 0);">);</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">CGFloat</span><span class="pln" style="color: rgb(0, 0, 0);"> y </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">CGRectGetMinY</span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">frame</span><span class="pun" style="color: rgb(102, 102, 0);">);</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">CGFloat</span><span class="pln" style="color: rgb(0, 0, 0);"> width </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">CGRectGetWidth</span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">frame</span><span class="pun" style="color: rgb(102, 102, 0);">);</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">CGFloat</span><span class="pln" style="color: rgb(0, 0, 0);"> height </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">CGRectGetHeight</span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">frame</span><span class="pun" style="color: rgb(102, 102, 0);">);</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">CGRect</span><span class="pln" style="color: rgb(0, 0, 0);"> frame </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">CGRectMake</span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="lit" style="color: rgb(0, 102, 102);">0.0</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">0.0</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> width</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> height</span><span class="pun" style="color: rgb(102, 102, 0);">);</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

不应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="typ" style="color: rgb(102, 0, 102);">CGRect</span><span class="pln" style="color: rgb(0, 0, 0);"> frame </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="kwd" style="color: rgb(0, 0, 136);">self</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">view</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">frame</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">CGFloat</span><span class="pln" style="color: rgb(0, 0, 0);"> x </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> frame</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">origin</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">x</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">CGFloat</span><span class="pln" style="color: rgb(0, 0, 0);"> y </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> frame</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">origin</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">y</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">CGFloat</span><span class="pln" style="color: rgb(0, 0, 0);"> width </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> frame</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">size</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">width</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">CGFloat</span><span class="pln" style="color: rgb(0, 0, 0);"> height </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> frame</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">size</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">height</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="typ" style="color: rgb(102, 0, 102);">CGRect</span><span class="pln" style="color: rgb(0, 0, 0);"> frame </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="typ" style="color: rgb(102, 0, 102);">CGRect</span><span class="pun" style="color: rgb(102, 102, 0);">){</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">origin </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">CGPointZero</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">size </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> frame</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">size </span><span class="pun" style="color: rgb(102, 102, 0);">};</span></code>

黄金路径

当使用条件语句编码时，左手边的代码应该是”

golden

” 或 “

happy

”路径。也就是不要嵌套if语句，多个返回语句也是OK。

应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="kwd" style="color: rgb(0, 0, 136);">void</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">someMethod </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">if</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(![</span><span class="pln" style="color: rgb(0, 0, 0);">someOther boolValue</span><span class="pun" style="color: rgb(102, 102, 0);">])</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">return</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">//Do something important  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

不应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="pun" style="color: rgb(102, 102, 0);">-</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="kwd" style="color: rgb(0, 0, 136);">void</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">someMethod </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">if</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">([</span><span class="pln" style="color: rgb(0, 0, 0);">someOther boolValue</span><span class="pun" style="color: rgb(102, 102, 0);">])</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">//Do something important  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

错误处理

当方法通过引用来返回一个错误参数，判断返回值而不是错误变量。

应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="typ" style="color: rgb(102, 0, 102);">NSError</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">error</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">if</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(![</span><span class="kwd" style="color: rgb(0, 0, 136);">self</span><span class="pln" style="color: rgb(0, 0, 0);"> trySomethingWithError</span><span class="pun" style="color: rgb(102, 102, 0);">:&</span><span class="pln" style="color: rgb(0, 0, 0);">error</span><span class="pun" style="color: rgb(102, 102, 0);">])</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">// Handle Error  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

不应该：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="typ" style="color: rgb(102, 0, 102);">NSError</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">*</span><span class="pln" style="color: rgb(0, 0, 0);">error</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">[</span><span class="kwd" style="color: rgb(0, 0, 136);">self</span><span class="pln" style="color: rgb(0, 0, 0);"> trySomethingWithError</span><span class="pun" style="color: rgb(102, 102, 0);">:&</span><span class="pln" style="color: rgb(0, 0, 0);">error</span><span class="pun" style="color: rgb(102, 102, 0);">];</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">if</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">error</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="com" style="color: rgb(136, 0, 0);">// Handle Error  </span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

在成功的情况下，有些Apple的APIs记录垃圾值(

garbage values

)到错误参数(如果

non-NULL

)，那么判断错误值会导致

false

负值和

crash

。

单例模式

单例对象应该使用线程安全模式来创建共享实例。

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="pun" style="color: rgb(102, 102, 0);">+</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">instancetype</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);">sharedInstance </span><span class="pun" style="color: rgb(102, 102, 0);">{</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">static</span><span class="pln" style="color: rgb(0, 0, 0);"> id sharedInstance </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="kwd" style="color: rgb(0, 0, 136);">nil</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">static</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">dispatch_once_t</span><span class="pln" style="color: rgb(0, 0, 0);"> onceToken</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
dispatch_once</span><span class="pun" style="color: rgb(102, 102, 0);">(&</span><span class="pln" style="color: rgb(0, 0, 0);">onceToken</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">^{</span><span class="pln" style="color: rgb(0, 0, 0);">
sharedInstance </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">[[</span><span class="kwd" style="color: rgb(0, 0, 136);">self</span><span class="pln" style="color: rgb(0, 0, 0);"> alloc</span><span class="pun" style="color: rgb(102, 102, 0);">]</span><span class="pln" style="color: rgb(0, 0, 0);"> init</span><span class="pun" style="color: rgb(102, 102, 0);">];</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">});</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="kwd" style="color: rgb(0, 0, 136);">return</span><span class="pln" style="color: rgb(0, 0, 0);"> sharedInstance</span><span class="pun" style="color: rgb(102, 102, 0);">;</span><span class="pln" style="color: rgb(0, 0, 0);">
</span><span class="pun" style="color: rgb(102, 102, 0);">}</span><span class="pln" style="color: rgb(0, 0, 0);"> </span></code>

这会防止possible and sometimes prolific crashes。

换行符

换行符是一个很重要的主题，因为它的风格指南主要为了打印和网上的可读性。

例如：

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="kwd" style="color: rgb(0, 0, 136);">self</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">productsRequest </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">[[</span><span class="typ" style="color: rgb(102, 0, 102);">SKProductsRequest</span><span class="pln" style="color: rgb(0, 0, 0);"> alloc</span><span class="pun" style="color: rgb(102, 102, 0);">]</span><span class="pln" style="color: rgb(0, 0, 0);"> initWithProductIdentifiers</span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);">productIdentifiers</span><span class="pun" style="color: rgb(102, 102, 0);">];</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

一行很长的代码应该分成两行代码，下一行用两个空格隔开。

<code style="margin: 0px; padding: 0px; font-size: 1em; font-family: Menlo, Monaco, Consolas, 'Courier New', monospace; color: rgb(199, 37, 78); background-color: transparent;"><span class="kwd" style="color: rgb(0, 0, 136);">self</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">productsRequest </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">[[</span><span class="typ" style="color: rgb(102, 0, 102);">SKProductsRequest</span><span class="pln" style="color: rgb(0, 0, 0);"> alloc</span><span class="pun" style="color: rgb(102, 102, 0);">]</span><span class="pln" style="color: rgb(0, 0, 0);">
initWithProductIdentifiers</span><span class="pun" style="color: rgb(102, 102, 0);">:</span><span class="pln" style="color: rgb(0, 0, 0);">productIdentifiers</span><span class="pun" style="color: rgb(102, 102, 0);">];</span><span class="pln" style="color: rgb(0, 0, 0);">  </span></code>

Xcode工程

物理文件应该与Xcode工程文件保持同步来避免文件扩张。任何Xcode分组的创建应该在文件系统的文件体现。代码不仅是根据类型来分组，而且还可以根据功能来分组，这样代码更加清晰。

尽可能在

target

的

Build
Settings

打开”

Treat Warnings as Errors

，和启用以下

additional
warnings

。如果你需要忽略特殊的警告，使用

Clang’s pragma feature

。