isBeingDismissed not set in viewWillDisappear: - iphone

Question

I have some code to clean up in my viewWillDisappear:, which I only want to use when the view is moving back to the parent view controller.
- (void)viewWillDisappear:(BOOL)animated
{
if ([self isMovingFromParentViewController] || [self isBeingDismissed]) {
NSLog(#"isMovingFromParentViewController or isBeingDismissed");
// clean up
}
[super viewWillDisappear:animated];
}
The view can be presented in two ways: it can be pushed by a navigation controller, or presented as a modal view controller (from the same navigation controller). If it's pushed, then popped (pressing the back button), my clean-up code runs. If it it presented as a modal view controller, then dismissed, the code doesn't run.
I dismiss like so:
[rootViewController dismissModalViewControllerAnimated:YES];
My question is: why isn't isBeingDismissed set when I dismiss my view controller?

Answer 1

If this is the first view controller in a modal navigation controller that's being dismissed, calling self.isBeingDimissed() from viewWillDisappear: returns false.
However, since the entire navigation controller is being dismissed, what actually works is self.navigationController?.isBeingDismissed(), which returns true.

Answer 2

As #Yuval Tal mentioned, this flag does not work when you're dismissing controller that is embeded inside navigation controller. Here's an extension that I use:
extension UIViewController
{
var isAboutToClose: Bool {
return self.isBeingDismissed ||
self.isMovingFromParent ||
self.navigationController?.isBeingDismissed ?? false
}
}
It can be easily extended when you find another case when standard .isBeingDismissed won't work. And if you find, let us, let me know in comments.

Answer 3

Your issue is how you are dismissing your modal view. How is rootViewController being defined?
When I call [self dismissModalViewControllerAnimated:YES] then [self isBeingDismissed] evaluates to true.
When I call [parentViewController dismissModalViewControllerAnimated:YES] then [self isBeingDismissed] evaluates to true, whereby parentViewController is the UIViewController that presented the modal view (note: not a UINavigationController).

Answer 4

If by some chance you came here trying to use isBeingDismissed on a non-modally presented view controller, you can always check the topViewController property of your navigationController, for instance:
if navigationController?.topViewController != self {
return
}

Answer 5

viewController.isBeingPresented == NO;
[rootVC presentViewController:viewController animated:NO completion:^{
viewController.isBeingPresented == NO;
viewController.isBeingDismissed == NO;
[viewController dismissViewControllerAnimated:NO completion:^{
viewController.isBeingDismissed == NO;
}];
viewController.isBeingDismissed == NO; // is not work
}];
viewController.isBeingPresented == YES; // is work
viewController.isBeingPresented == NO;
[rootVC presentViewController:viewController animated:NO completion:^{
viewController.isBeingPresented == NO;
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
viewController.isBeingDismissed == NO;
[viewController dismissViewControllerAnimated:NO completion:^{
viewController.isBeingDismissed == NO;
}];
viewController.isBeingDismissed == YES; // is work
});
}];
viewController.isBeingPresented == YES; // is work