title: UINavigationController – Override Back button action
body: <p>I have a view controller in a navigation stack that represents a form that the user can fill out. The form has a handful of text fields and an "Apply" button at the bottom. If the user taps the native back button on the navigation bar after entering some information, I want the user to be prompted with a confirmation message: "Your changes have not been saved. Are you sure you want to go back?" But I'm not sure of a way I can "legally" override the action of the native back button. Is this possible?</p>