title: Listener for "Going back" in Navigation Controller
body: <p>I found many old answers for this questions, but they all are 2+ years old.</p>
  
  <p>I would like to add listener for the left button - the "back" one. I would like to show UIAlertView and then wait for response - YES/NO.</p>
  
  <p>Is it possible in newer SDK?</p>