title: Get the frame of UIBarButtonItem in Swift?
body: <p>how could I get the frame of a rightbarbuttonItem in swift? I found this : <a href="https://stackoverflow.com/questions/14318368/uibarbuttonitem-how-can-i-find-its-frame">UIBarButtonItem: How can I find its frame?</a> but it says cannot convert NSString to UIView, or cannot convert NSString to String :</p>
  
  <pre><code>let str : NSString = "view" //or type String
  let theView : UIView = self.navigationItem.rightBarButtonItem!.valueForKey("view")//or 'str'
  </code></pre>
  
  <p>The goal is to remove the rightBarButtonItem, add an imageView instead, and move it with a fadeOut effect.</p>
  
  <p>Thanks</p>