Swift version: 5.1
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.
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Available from iOS 2.0
This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.