iOS: how to detect if viewcontroller appears after pop or dismiss

Question

I have a view controller VC1 and I am doing following two operations on it:

1. Push another view controller VC2 from VC1's navigation controller by calling

[VC1.navigationController pushViewController: animated:YES];

2. Present another view controller VC3 from VC1 by calling.

   UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController:VC3]; [VC1 presentViewController:navController animated:YES completion:nil];

Now when I am coming from VC2 to VC1 I am calling

[VC2.navigationController popViewControllerAnimated:YES];

and from VC3 to VC1 I am calling

[VC3.navigationController dismissViewControllerAnimated:YES completion:nil];

My question is when I am coming back to VC1 how do I know that whether I am coming from VC2(by dismissing) or VC3(by popping)?

Note: VC1 is loaded as child view controller inside a parent view controller VC4.

Answer 1

The best way would be to have the childViewController call back to the presenting view controller. By doing this the childViewController will not need to know the implementation details of whether it was presented modally or in a navigation stack etc.

With blocks it would look something like

@interface VC2 : UIViewController

@property (nonatomic, copy) void (^completion)(VC2 *viewController);

@end

You would set this block up something like this

VC2 *viewController = VC2.new;
viewController.completion = ^(VC2 *viewController) {
  [viewController.navigationController popViewControllerAnimated:YES];
};

[VC1.navigationController pushViewController:viewController animated:YES];

Now where you was previously calling

[VC2.navigationController popViewControllerAnimated:YES];

You instead call

self.completion(self);

You put any logic you want to be associated with coming back from a specific viewController inside the completion handler