error:assign attribute must be unsafeunretained

今天在使用协议的过程中。偶然发现这样使用

 

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@interface AppDelegate (){     id<chatdelegate>  testdelegate; } @property (nonatomic , assign) id<chatdelegate> testdelegate;   @end   @implementation AppDelegate @synthesize testdelegate; </chatdelegate></chatdelegate>

会报错：

 

Existing instance variable 'delegate' for property 'delegate' with assign attribute must beunsafe unretained

改动成：

 

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@interface AppDelegate (){    __unsafe_unretained id<chatdelegate>  testdelegate; } @property (nonatomic , assign) id<chatdelegate> testdelegate;   @end   @implementation AppDelegate @synthesize testdelegate; </chatdelegate></chatdelegate>

就好了，这仅仅是为了相容iOS4下面的版本号