title: How to make extension for multiple classes Swift
body: <p>I have an extension:</p>
  
  <pre><code>extension UILabel {
      func animateHidden(flag: Bool) {
          self.hidden = flag
      }
  }
  </code></pre>
  
  <p>I need to make the same one for <code>UIImageView</code> but I don't want to copy that whole code. Is it possible to make an extension for multiple classes?</p>
  
  <p>Thanks.</p>