title: Change back item title with push Segue
body: <p>I'm using a push segue for showing a new ViewController in my Storyboard. By default, the back bar item on the pushed navigation controller has the title of the "previous" (underlaying) controller.</p>
  
  <p>In order to change the title of the back bar item to, e.g., "Back" I implemented the following in the ViewController which gets pushed:</p>
  
  <pre class="lang-c prettyprint-override"><code>- (void)viewDidLoad {
      [super viewDidLoad];
  
      self.navigationItem.backBarButtonItem.title = @"Back";
  }
  </code></pre>
  
  <p>But this doesn't change the title of the back bar item. I've also tried to use a newly created UIBarButtonItem with the same result: the back bar item doesn't change.</p>
  
  <p>Another approach was the set the back bar item like in <code>prepareForSegue</code> in the controller where the segue is executed.</p>
  
  <pre class="lang-c prettyprint-override"><code>- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender 
  {
  
      if ([[segue identifier] isEqualToString:@"pushViewController"]) {
          UIViewController *viewController = [segue destinationViewController];
          viewController.navigationItem.backBarButtonItem.title = @"Back";
      }
  }
  </code></pre>
  
  <p>With the same result: the back bar item title doesn't change. So how can i easily change the title of the back bar item? Thanks in advance!</p>