Iphone 确认反向导航

我只想确认一个视图的向后导航。特定视图是UICollectionViewController。我知道我在if语句中的确切编码不正确。我不太清楚怎么做。帮我填空好吗

CollectionViewController.m

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.

    BOOL isThisViewACollectionView = YES;

}

-(void) viewWillDisappear:(BOOL)animated {
    if ([self.navigationController.viewControllers indexOfObject:self]==NSNotFound) {
        // back button was pressed.  We know this is true because self is no longer
        // in the navigation stack.
        if (isThisViewACollectionView) {
            UIAlertView *cameraAlertView = [[UIAlertView alloc] initWithTitle:@"Camera Not Available" message:@"The camera feature isn't available on your device." delegate:nil cancelButtonTitle:@"Okay" otherButtonTitles:nil];
            [cameraAlertView show];
        }
    }else{
        [super viewWillDisappear:animated];
    }
}

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逻辑上有问题,， 当您已删除viewcontroller时，将调用以下语句

   if ([self.navigationController.viewControllers indexOfObject:self]==NSNotFound) {

    }

因此，更好的解决方案是在“上面（之前）”的某个位置保存一个值，该值将消失，从而知道viewcontroller是否为uicollectionView（比方说BOOL）

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假设此值为真，请提醒用户（填写缺失的代码）。

您能给我举个例子吗？在viewDidLoad中设置一个BOOL值-例如BOOL isThisViewACollectionView=YES；您缺少的代码是if（isThisViewACollectionView）{//将出现一个警报}更新的代码。它在viewWillDissapear中表示isThisViewACollectionView是一个未声明的标识符