Written by Paul Hudson @twostraws
You probably already know that viewWillDisappear() is called when a view controller is about to go away, and that's also called when the user taps the Back button in a navigation controller. Problem is, the same method is called when the user moves forward, i.e. when you push another view controller onto the stack.
The solution is simple: create a Boolean property called goingForwards in your view controller, and set it to true before pushing any view controller onto the navigation stack, then set it back to false when the view controller is shown again. This way, when viewWillDisappear() is called you can check goingForwards: if it's false, the user tapped Back.
Available from iOS 2.0
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