title: swift: Font of title in navigation bar
body: <p>in AppDelegate.swift I have following code: </p>
  
  <pre><code>let nav1 = UINavigationController()
      let mainView = ViewController(nibName: nil, bundle: nil) //ViewController = Name of your controller
      nav1.viewControllers = [mainView]
  nav1.navigationBar.topItem?.title = "JT"
      nav1.navigationController?.navigationBar.titleTextAttributes = [ NSFontAttributeName: UIFont(name: "AvenirNext-UltraLight", size: 24)!,  NSForegroundColorAttributeName: UIColor.whiteColor()]
  </code></pre>
  
  <p>But last line doesn't change font of title of nav bar
  What i should do?</p>