title: Change global UIBarButtonItem appearance
body: <p>I am using Swift to build an iOS application and would like to change the global <strong><code>appearance</code></strong> of <code>UIBarButtonItem</code>. I am doing this in <code>didFinishLaunchingWithOptions</code>.</p>
  
  <p>Apple's documentation says this:</p>
  
  <pre><code>func setTitleTextAttributes(_ attributes: [String : AnyObject]?, forState state: UIControlState)
  </code></pre>
  
  <p>for <code>UIBarItem</code>. But when I try to do this, it only expects <code>self: UIBarItem</code>. Has anyone else encountered this? Is it a bug in Xcode or am I doing something wrong?</p>