title: Swift: UIButton on UILabel
body: <p>In some circumstance, I have to make a UILabel clickable.
  I tried many answers from stackOverflow to make the UIlabelClickable, but they were not working.</p>
  
  <p>So eventually, I decided to position UIButton on the UILabel, and make the button transparent.</p>
  
  <p>However, although the button correctly position on top of the Label, clicking the button does not interact. Any idea?</p>
  
  <p>Thanks</p>
  
  <p>Edit: In addition, there are two views, say view1 and view2. Due to structure of my app, I placed the UIButton and UILabel on view 2, and then placed view 2 on view1.
  So: </p>
  
  <pre><code>view2.addSubview(button)
  view1.addSubview(view2)
  </code></pre>