title: Instance variables are nil after I try to set them
body: <p>can't understand what's wrong here. I want to set some instance variables for view controller:</p>
  
  <pre><code>    private func simpleViewControllerAtIndex(index: Int) -&gt; UIViewController! {
      let controller: SimpleTutorialController = storyboard?.instantiateViewControllerWithIdentifier("SimpleTutorialController") as! SimpleTutorialController
      let mainText = "simple_main_\(index + 1)".localized
      let detailText = "simple_detail_\(index + 1)".localized
      print(mainText)
      print(detailText)
      controller.mainText? = mainText
      controller.detailText? = detailText
      print(controller.mainText)
      print(controller.detailText)
      return controller
  }
  </code></pre>
  
  <p>and in logs I see something strange:</p>
  
  <pre><code>Aprendizagem
  Palavra
  nil
  nil
  </code></pre>
  
  <p>How to solve the issue?</p>