title: How to dismiss UIAlertController when tap outside the UIAlertController?
body: <p>How to dismiss <code>UIAlertController</code> when tap outside the <code>UIAlertController</code>? </p>
  
  <p>I can add a <code>UIAlertAction</code> of style <code>UIAlertActionStyleCancel</code> to dismiss the <code>UIAlertController</code>.</p>
  
  <p>But I want to add the function that when user tap outside the <code>UIAlertController</code> the <code>UIAlertController</code> will dismiss. How to do that? Thank you.</p>