Is the UIViewController calling the method presentViewController removed from the memory?

Question

Supposedly I have a UIViewController A and a UIViewController B. From A, I call the method presentViewController:B. When B shows up, what happens to A? Is it removed from the memory? If not, what method should I call to delete it?

If my UI flow is like this, A->B->A->B->A->B->... and so on, how to prevent the memory from increasing accordingly?

Answer 1

When you use the presentViewController:animated:completion: method from controller A to present controller B modally, what happens is that the presentedViewController property of A is set to controller B, and the presentingViewController property of B is set to A. Thus, both controllers are kept in memory while the presentation is taking place.

When you go from B to A, you call dismissViewControllerAnimated:completion: on A via the presentingViewController property of B, like this:

[self.presentingViewController dismissViewControllerAnimated:YES completion:nil];

(You can also call [self dismissViewControllerAnimated:YES completion:nil] and the system will automatically forward the request to the presenting view controller.)

After that, the presentedViewController property of A will be set to nil and, consequently, it will be subject to memory deallocation by the system, provided that there isn't any other strong pointer pointing to it.

Answer 2

No, A won't be removed from memory. And if you want to alternate between A and B you can either:

• use a UINavigationController and push B, then pop it off again and you're back at A
• or make B the new root controller of your window and then A again and add a proper transition
• or use a as the root and present B. Then dismiss B and you're back at A.

Answer 3

The UIViewController will stay in memory unless you popped it.

Use push & pop instead of just pushing new UIViewControllers.

Instead of this A->B->A->B->A->B->

You'll get this A<->B

Answer 4

Have a root view controller when ever A completes it's task let your root view is responsible of removing A and and presenting B. Like wise when B finishes its task alert your root view to remove B and show A again.

Answer 5

It won't be released automatically. You can release it manually by using dismissModalViewControllerAnimated.

Here is a very good tutorial to see this : Link