title: Unwind segue doesn't work SWIFT
body: <p>I have a navigation controller, with a table view. When I press a cell, the detail view controller opens.</p>
  
  <p>In my root view controller I have : </p>
  
  <pre><code>override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
  
      if segue.identifier == "detailview" {    
          var destination:DetailViewController = segue.destinationViewController as DetailViewController
          destination.delegate=self   
      }
  }
  </code></pre>
  
  <p>In my detail view controller I have a back button :</p>
  
  <pre><code>@IBAction func back() {        
      self.navigationController?.popViewControllerAnimated(true)    
  }
  </code></pre>
  
  <p>The issue is, after 2 go to and return, my app crashes when I go back on the root view controller pressing back button. The console doesn't give me errors. It just crashes.</p>
  
  <p>I think I have forgotten to unwind the segue. 
  So in my detail view controller I added :</p>
  
  <pre><code>@IBAction func unwindToViewController(segue: UIStoryboardSegue) {
      println("unwind function")
  }
  </code></pre>
  
  <p>I connect this function to my back button with "exit" in my storyboard.</p>
  
  <p>When I run my app, If I press on the back button, the console doesn't display my print "unwind function", so unwindToViewController isn't called. Why ?</p>
  
  <p>And my app still crashes...</p>