I need to execute an action (emptying an array), when the back button of a UINavigationController is pressed, while the button still causes the previous ViewController on the stack to appear. How could I accomplish this using swift? 
I need to execute an action (emptying an array), when the back button of a UINavigationController is pressed, while the button still causes the previous ViewController on the stack to appear. How could I accomplish this using swift?
