Change value in parentViewController when back button in childViewController was pressed

Question

I need something like this self.parentViewController.someValue = 20 . Is it possible? I use UINavigationBar. And I want when user tapped on back button, some value in my main controller changed.

Answer 1

I can think of four ways to do this and there are probably more that aren't coming to mind.

1) Update a data model and have the parent controller be an observer of the change using KVO.

2) Send a notification when the second controller is going away and have the parent listen for it.

3) Create a delegate protocol that lets the second controller reference a parent method directly.

4) Use the parent's viewWillAppear: and check the isMovingToParentViewController property for whether it's just re-appearing.

You have lots of choices! :)