Updating view A that was behind view B after the back button in the navigation bar is pressed and view B is popped

I have two views A & B in order to go from A to B I'm just pushing the new view, in view B I preform some actions that update the badgeValue of a UIBarButton item of my navigation bar. (Like adding an item to the shopping cart)

When I go back to view A using the navigationBar Back button the UIBarButton item shows the previous badgeValue, instead of the updated one, I guess this happens because when you press the back button view B is popped revealing view A which is left as it was without any changes so, I need a way to tell view A to update itself after returning.

If instead of going back to view A I go back to the rootViewController the badgeValue is updated, I guess that when I go to the rootViewController the code in viewDidLoad is read and the badgeValue is updated.

Any ideas on how to update a view that was behind another that was just popped?

EDIT

@silicon_valley answer is correct but it won't work with MikeMTOL's library because it's buggy, for Swift users I'd recommend these extensions instead. -> link

You can add your code to update the badge value in viewWillAppear. That will make sure the value is updated every time the view will come back on the screen (and not just the first time it is created).