title: PopViewControllerAnimated not working. No ref to calling VC
body: <p>I have a <code>UITabBarViewController</code> containing 4 individual ViewControllers. Each VC has a <code>UIBarButtonItem</code> on their <code>NavigationBar</code> to take you to a "postPage". You get to the post page by using this code, which presents the embedded <code>NavigationController</code></p>
  
  <pre><code>- (void)postInvoked:(UIBarButtonItem *)sender
  {
      UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
      UIViewController *postPage = [storyboard instantiateViewControllerWithIdentifier: @"postPageLead"];
      [self presentViewController:postPage animated:YES completion:nil];
  }
  </code></pre>
  
  <p>Then in the <code>PostViewController.m</code>, I have an <code>IBAction</code> that is triggered when the user clicks the <code>UIBarButtonItem</code> named "Back":</p>
  
  <pre><code>- (IBAction)backOnPost:(UIBarButtonItem *)sender
  {
      [self.parentViewController.navigationController popViewControllerAnimated:YES];
  }
  </code></pre>
  
  <p>This isn't working.. Keep in mind that the calling VC isn't remembered once you arrive at the postpage. How do I traverse back to the original calling <code>ViewController</code>?(how do I reference the caller, and is popViewControllerAnimated: necessary?)</p>