title: Action to Navigation bar back button
body: <p>I want to show an alert with Confirmation when user clicks on back button. This is how I'm trying to add action.</p>
  
  <pre><code>self.navigationItem.hidesBackButton = true
  let newBackButton = UIBarButtonItem(title: "&lt;", style: UIBarButtonItemStyle.plain, target: self, action: #selector(ViewController.save(sender:)))
  self.navigationItem.leftBarButtonItem = newBackButton
  </code></pre>
  
  <p>This is working fine but I want the default back button image in it and not the custom title. How to do that ?</p>
  
  <p>I tried following code as well :</p>
  
  <pre><code>self.navigationItem.backBarButtonItem?.action = #selector(ViewController.save(sender:))
  </code></pre>
  
  <p>...but the action is not performed, too. </p>