ios - 如何在 if 语句中检查 NSNotification

Question

我正在尝试运行以下代码，除非NSNotification发送了 a 。我不知道如何将NSNotificationif 语句放入：

if (!self.subViewControllerProv) {
    self.subViewControllerProv = [[ProvViewController alloc] init];
}


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

回顾一下：如果观察到了NSNotification消息，那么如果没有观察到alloc则init不要ProvViewController。

Answer 1

尝试添加一个实例变量来保存通知是否已触发的标志，在 -handleNotification: 中设置标志，然后在适当的时候检查。

- (void)handleNotification:(NSNotification*)notification {
    _notificationWasPosted = YES;
}

...

if (!_notificationWasPosted && !self.subViewControllerProv) {
    self.subViewControllerProv = [[ProvViewController alloc] init];
}

Answer 2

那么如何做这样的事情：

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

进而

-(void) handleNotification {
    //BOOL _hasBeenSent in your interface
    _hasBeenSent = YES;
}

然后在你的代码中

if(_hasBeenSent) {
    NSLog(@"The notification has been sent!");
}