ios 开发常用小知识

1.//计算文本长度

- (CGFloat)calculateTextNecessaryWidthWithString:(NSString *)string withFontSize:(CGFloat)size {

    CGRect contentSize = [string
boundingRectWithSize:CGSizeMake(8000, size)
options:NSStringDrawingUsesLineFragmentOrigin
attributes:@{NSFontAttributeName:[UIFont
systemFontOfSize:size]}
context:nil];

    return contentSize.size.width;

}

2.//计算文本高度

- (CGFloat)calculateTextNecessaryHightWithString:(NSString *)string withTextWidth:(CGFloat)width withFontSize:(CGFloat)size{

    CGRect contentSize = [string
boundingRectWithSize:CGSizeMake(width,
8000)
options:NSStringDrawingUsesLineFragmentOrigin
attributes:@{NSFontAttributeName:[UIFont
systemFontOfSize:size]}
context:nil];

    return contentSize.size.height;

}

3./*! @brief

 *  判断该字符串中是否存在指定的字符串（兼容iOS7）

 *

 *  @param str
指定的字符串

 *

 *  @return <#return value description#>

 */

-(BOOL)extensionWithContainsString:(NSString *)str
NS_AVAILABLE(10_10,
7_0){

    return __IPHONE_SYSTEM_VERSION <
8 ? ([self
rangeOfString:str].location !=
NSNotFound) : [self
containsString:str];

}

4.//去除指定视图控制器的状态栏
在对应控制器里设置

-(BOOL)prefersStatusBarHidden{

    return
YES;

}
视然后还需在pilot文件里设置View controller-based status bar appearance 为YES。

5.设置定位提示语（允许应用内使用定位）
在plist中设置 NSLocationAlwaysUsageDescription 为YES

然后还需调用  requestWhenInUseAuthorization
6.检测手机系统版本 [[UIDevice
currentDevice].systemVersion floatValue] 

  检测app本地版本 [[NSBundle mainBundle] objectForInfoDictionaryKey:@"CFBundleShortVersionString"]