今天在使用协议的过程中，偶然发现这样使用
@interface AppDelegate (){
id<ChatDelegate> testdelegate;
}
@property (nonatomic , assign) id<ChatDelegate> testdelegate;
@end
@implementation AppDelegate
@synthesize testdelegate;
Existing instance variable ‘delegate‘ for property ‘delegate‘ with assign attribute must be unsafe unretained
修改成：
@interface AppDelegate (){
__unsafe_unretained id<ChatDelegate> testdelegate;
}
@property (nonatomic , assign) id<ChatDelegate> testdelegate;
@end
@implementation AppDelegate
@synthesize testdelegate;
参考：http://www.cnblogs.com/lyanet/archive/2013/05/07/3064290.html
ios 协议（delegate）使用过程中遇到assign attribute must be unsafeunretained
原文：http://blog.csdn.net/lv_ruanruan/article/details/44751147