title: Swift cast fails
body: <p>So I'm writing this segue method in Swift, but when I unwrap controller, it is always none. Without the <code>as?</code> it just downright fails at runtime. Whats going on?</p>
  
  <pre><code>override func prepareForSegue(segue : UIStoryboardSegue!, sender: AnyObject!) {
      if(segue.identifier == "showCoursesSegue") {
          var controller = segue.destinationViewController as? EditViewController
          controller!.test = true 
      }
  
  }
  </code></pre>