@property （nonatomic， retain）

1.readonly表示这个属性是只读的，就是只生成getter方法，不会生成setter方法．

2.readwrite，设置可供访问级别

3.retain，是说明该属性在赋值的时候，先release之前的值，然后再赋新值给属性，引用再加1。

4.nonatomic，非原子性访问，不加同步，多线程并发访问会提高性能。注意，如果不加此属性，则默认是两个访问方法都为原子型事务访问。

@property(nonatomic, retain) NSString *text; translates as
“I have a member variable of type NSString* named ‘text’. I will want a getter/setter pair that uses the retain/release procedure.”

@property(nonatomic, assign) int value; translates as
“I have a member variable of type int named ‘value’. I will want a getter/setter pair that doesn’t use the retain/release procedure – just assign it.”

加上一段参考代码。。。


代码

@property(nonatomic, retain) UITextField * userName编译时自动生成的代码

- (UITextField * ) userName {
return userName;
}

- ( void ) setUserName:(UITextField * )userName_ {
[userName release];
userName = [userName_ retain];
}

@property(retain) UITextField * userName自动生成的代码

- (UITextField * ) userName {
UITextField * retval = nil;
@synchronized(self) {
retval = [[userName retain] autorelease];
}
return retval;
}

- ( void ) setUserName:(UITextField * )userName_ {
@synchronized(self) {
[userName release];
userName = [userName_ retain];
}
}