title: Adding am UIPageViewController in front of a UIViewController
body: <p>When my app starts for the first time it should display a tutorial, which are some screens with a semitransparent background, in front of the first app screen.</p>
  
  <p>I tried creating an UIPageViewController object, adding its view as subview of the current screen (<code>self.view.addSubview(tutorialViewController.view)</code>) and the screen is displayed, however when I swipe the <code>UIPageViewController</code> is not responding the event.</p>
  
  <pre><code>class TutorialViewController:UIPageViewController, UIPageViewControllerDataSource {
  var tutorialsViewControllers = [UIViewController]()
  
  
  override func viewDidLoad() {
      super.viewDidLoad()
      tutorialsViewControllers.append(Tutorial1ViewController())
      tutorialsViewControllers.append(Tutorial2ViewController())
      tutorialsViewControllers.append(Tutorial3ViewController())
      tutorialsViewControllers.append(Tutorial4ViewController())
      tutorialsViewControllers.append(Tutorial5ViewController())
      self.setViewControllers([tutorialsViewControllers.first!], direction: .Forward, animated: false) { (complete) -&gt; Void in
      }
      self.dataSource = self
  }
  
  func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -&gt; UIViewController? {
      if let position = find(self.tutorialsViewControllers, viewController)
          where position &gt; 0
      {
          return self.tutorialsViewControllers[position - 1]
      }
      return nil
  }
  func pageViewController(pageViewController: UIPageViewController, viewControllerAfterViewController viewController: UIViewController) -&gt; UIViewController?{
      if let position = find(self.tutorialsViewControllers, viewController)
          where position &lt; self.tutorialsViewControllers.count - 1
      {
          return self.tutorialsViewControllers[position - 1]
      }
      return nil
  }
  }
  </code></pre>
  
  <p>That's the view controller code</p>
  
  <pre><code>let tutorialViewController = TutorialViewController()        
  self.view.addSubview(tutorialViewController.view)
  </code></pre>