Objective-c – Checking if a UIViewController is about to get Popped from a navigation stack

To find out when it's pushed, you can use the

UINavigationControllerDelegate

and implement

- (void)navigationController:(UINavigationController *)navigationController 
      willShowViewController:(UIViewController *)viewController
                    animated:(BOOL)animated

This method will fire whenever the viewcontroller is pushed into the navigation stack, and whenever the viewcontroller on top of it is popped off, thus revealing it again. So you have to use a flag to figure out if it's been initialized yet, if it hasn't means it just was pushed.

To find out when it's been popped, use this answer:

viewWillDisappear: Determine whether view controller is being popped or is showing a sub-view controller

I know an answer has been accepted over two years ago, however this answer is incomplete.

There is no way to do what you're wanting out-of-the-box

This is technically correct because the UINavigationController API doesn't offer any options for this. However by using the CoreAnimation framework it's possible to add a completion block to the underlying animation:

[CATransaction begin];
[CATransaction setCompletionBlock:^{
    // handle completion here
}];

[self.navigationController popViewControllerAnimated:YES];

[CATransaction commit];

The completion block will be called as soon as the animation used by popViewControllerAnimated: ends. This functionality has been available since iOS 4.