title: Set label text in navigation title when scrolling
body: <p>In the storyboard, I have a label and many other objects in a <code>UIScrollView</code>. (The <code>UIScrollView</code> is in the view).</p>
  
  <p>I want to set the navigation bar's title to the title of the label when the label scrolls past it. </p>
  
  <p>I've tried this code but it doesn't work:</p>
  
  <pre><code>func scrollViewDidScroll(_ scrollView: UIScrollView) {
      if(self.lbl.frame.origin.x==60) {
          self.navigationController!.navigationBar.topItem!.title = lbl.text
      }
  }
  </code></pre>
  
  <p>What should i do? I am new to Swift.</p>