title: Mask a view in Objective-C
body: <p>In <strong>ActionScript 3</strong> we can apply a mask of to a visual object like this:</p>
  
  <pre><code>SomeVisualObject.mask = maskShapeObject; 
  </code></pre>
  
  <p>How can I achieve similar result in <strong>Objective-C</strong>? Assume I have two <code>UIImageView</code> objects, I want something like this:</p>
  
  <pre><code>imageView1.mask = imageView2;
  </code></pre>
  
  <p>How can I use one <code>UIImageView</code> to mask, or clip the shape of, another?</p>