title: TextField in Navigation Bar
body: <p>I'm trying to put UITextField instead of Navigation Title:</p>
  
  <pre><code>override func viewDidLoad() {
      super.viewDidLoad()
  
      let textField = UITextField()
      textField.text = "Title"
      self.navigationItem.titleView = textField
  }
  </code></pre>
  
  <p>and when I run the app I see text "Title", but when I try to edit this text field text become invisible.</p>