title: add/hide UITabBarItem
body: <p>I have a UITabBarController and would like to add a tab, with the ability to make it disappear. I added 2 tabs with XCode. You can add a third tab by program?
  I know a command like:</p>
  
  <pre><code>  [self setViewControllers: [NSArray arrayWithObjects: x1, nil] animated: NO];
  </code></pre>
  
  <p>You can retrieve the array that uses XCode to add a third view?
  thanks</p>
  
  <hr>
  
  <p>I can not load the view with the code. I created a view controller from the storyboard, when I try to load it from code I get a black screen, use this code:</p>
  
  <pre><code>ViewControllerA *x1 = [[ViewControllerA alloc] init];
  [self setViewControllers:[NSArray arrayWithObjects: x1, nil] animated:NO];
  </code></pre>