title: Return instancetype in Swift
body: <p>I'm trying to make this extension:</p>
  
  <pre><code>extension UIViewController
  {
      class func initialize(storyboardName: String, storyboardId: String) -&gt; Self
      {
          let storyboad = UIStoryboard(name: storyboardName, bundle: nil)
          let controller = storyboad.instantiateViewControllerWithIdentifier(storyboardId) as! Self
  
          return controller
      }
  }
  </code></pre>
  
  <p>But I get compile error:</p>
  
  <blockquote>
    <p>error: cannot convert return expression of type 'UIViewController' to
    return type 'Self'</p>
  </blockquote>
  
  <p>Is it possible? Also I want to make it as <code>init(storyboardName: String, storyboardId: String)</code></p>