UIPreviewAction *delete = [UIPreviewAction actionWithTitle:@"Delete" style:UIPreviewActionStyleDestructive handler:^(UIPreviewAction * _Nonnull action, UIViewController * _Nonnull previewViewController)
    {

//create alertController
...

// 1. present alertController:
[self presentViewController:alertController animated:YES completion:nil];

// 2. Alternatively tried to present alertController using keyWindow
UIViewController *top = [UIApplication sharedApplication].keyWindow.rootViewController;
[top presentViewController:alertController animated:YES completion: nil];

//3. notify the presenting view controller that the user has deleted the image and set up an alert to occur after the peek view closes.

[[NSNotificationCenter defaultCenter] postNotificationName:@"deleteAlert" object:nil];
}