title: How to Change back button title on navigation controller in swift3?
body: <p>I want to change the title of backbutton to any name in swift 3.I tried many ways but none of them worked for me.</p>
  
  <pre><code>self.navigationItem.backBarButtonItem?.title="Title"
  self.navigationController?.navigationItem.backBarButtonItem?.title="Title"
  </code></pre>
  
  <p>Just for information i have written below code in appdelegate.</p>
  
  <pre><code>let backImage : UIImage = UIImage(named:"backArrow")!
  UINavigationBar.appearance().barTintColor = UIColor(red: 0.0/255.0, green: 0.0/255.0, blue: 0.0/255.0, alpha: 1.0)
  UINavigationBar.appearance().tintColor = UIColor.white
  UINavigationBar.appearance().backIndicatorImage = backImage
  UINavigationBar.appearance().backIndicatorTransitionMaskImage = backImage
  UINavigationBar.appearance().titleTextAttributes = [NSForegroundColorAttributeName : UIColor.white]
  UIBarButtonItem.appearance().setBackButtonTitlePositionAdjustment(UIOffsetMake(0, 0), for: .default)
  IQKeyboardManager.sharedManager().enable = true
  self.window?.backgroundColor = UIColor.white
  </code></pre>