title: Dynamically change NavigationBar Back Button Text from presented ViewController
body: <p>I'm trying to change the back button text on a UINavigationBar upon receiving something from the network - basically replicating iMessage/FB Messenger by adding a new message count to the back button text ie. &lt; Back (1) or &lt; Messages (2)</p>
  
  <p>I can change the back button text from the presented ViewController (in viewDidLoad)</p>
  
  <pre><code>UIBarButtonItem *barButton = [[UIBarButtonItem alloc] init];
  barButton.title = @"Back";
  self.navigationItem.backBarButtonItem = barButton;
  </code></pre>
  
  <p>But when I try to use that same code in another method that is called upon receiving a new message, the back button text doesn't change.</p>
  
  <p>Any idea how I can change the back button text from the ViewController <strong>after it is presented</strong>? </p>