//建立通知 

    NSNotification * notification = [NSNotification notificationWithName:@"tongzhi" object:nil userInfo:nil];

//通過通知中心傳送通知

    [[NSNotificationCenter defaultCenter]postNotification:notification];

//註冊（接收通知）

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(tongzhi) name:@"tongzhi" object:nil];

//用完以後移除通知

[[NSNotificationCenter defaultCenter]removeObserver:self name:@"tongzhi" object:nil];