title: Callback method for presentViewController
body: <p>I'm having trouble with presentViewController method and its last parameter.</p>
  
  <pre><code>[self presentViewController:navigationController animated:YES completion:nil];
  </code></pre>
  
  <p>I'm new in objective-c syntax and can't find out what object should I pass to 'completion' parameter. (also didn't find any examples that use it)</p>
  
  <p>I want to have callback method when my presented View Controller dismisses.</p>
  
  <p>Thanks,</p>
  
  <p>Milos</p>