NSNotification(通知)

//创建一个消息对象
NSNotification * notice = [NSNotification notificationWithName:@"notification" object:nil userInfo:@{@"key":@"value"}];
//发送消息
[[NSNotificationCenter defaultCenter]postNotification:notice];

//获取通知中心单例对象
NSNotificationCenter * center = [NSNotificationCenter defaultCenter];
//添加当前类对象为一个观察者，name和object设置为nil，表示接收一切通知
[center addObserver:self selector:@selector(notice:) name:@"notification" object:nil];

-(void)notice:(NSNotification *)sender{
NSLog(@"%@",sender.userInfo[@"key"]);
}