Presenting an alert from a view controller that has closed

Question

I have an iOS Objective-C application in which I am attempting to show a UIAlertController, from a UIViewController which is in the process of closing. I have tried adding this common workaround in AppDelegate:

- (UIViewController *)currentTopViewController
{
   UIViewController *topVC = [[[[UIApplication sharedApplication] delegate] window] rootViewController];
   while (topVC.presentedViewController)
   {
     topVC = topVC.presentedViewController;
   }
  return topVC;
}

Called with:

[appDelegate.currentTopViewController presentViewController:alert animated:YES completion:nil];

However this error is still appearing:

Warning: Attempt to present UIAlertController on MyViewController whose view is not in the window hierarchy!

Can anyone advise?

You should send a notification (or use delegation, etc.) to the parent viewcontroller and present it from there — nathan, Jul 27 '17 at 23:11
@nathan Could you provide an example of using a notification? — user2181948, Jul 27 '17 at 23:35
Example of delegation: https://stackoverflow.com/a/33229483/2124535, NotificationCenter example: https://stackoverflow.com/a/29738348/2124535 — nathan, Jul 27 '17 at 23:47

score 0 · Answer 1 · answered Jul 28 '17 at 00:22

If you want to display an alert upon closing a viewcontroller, then you can just implement dismiss with completion block and display it there. For example:

[self dismissViewControllerAnimated:YES completion:^(void) {
  // UIAlertController code here

}];

score 0 · Answer 2 · edited Feb 26 '23 at 09:02

0

You can use UIWindow with a transparent UIViewController and then presenting the UIAlertController on it. Below link provides a category on UIAlertController that has a show method in Objective-C. You can use it.

Link: How to present UIAlertController when not in a view controller?

edited Feb 26 '23 at 09:02

Glorfindel

21,988
13
81
109

answered Jul 28 '17 at 03:13

Asif Raza

836
12
29

Presenting an alert from a view controller that has closed

2 Answers2