iphone - 关闭 UIViewController 时调用的方法？

Question

当当前 View Controller 被解除(弹出或解除ModalDialog)时，是否有一种通用的最佳实践方法可以得到通知？我不能使用 -viewWillDisappear:，因为当另一个 viewController 被推到当前 viewController 之上时也会调用它。

Answer 1

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    if (self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]) {
        [self addObserver:self forKeyPath:@"parentViewController" options:0 context:NULL];
    }
    return self;
}


- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    if ([@"parentViewController" isEqualToString:keyPath] && object == self) {
        if (!self.parentViewController)
            NSLog(@"Dismissed");
    }
}

- (void)dealloc
{
    [self removeObserver:self forKeyPath:@"parentViewController"];
    [super dealloc];
}