title: How to push new VC by swiping left in last UIPageViewController
body: <p>Is there any way to handle swipe left in last UIPageViewController?
  Basically I have 3 intro screens and the last screen has a button to go to the app. I want to add the ability to do the same by swiping left.</p>
  
  <p>my code:</p>
  
  <pre><code>func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -&gt; UIViewController? {
      let vc =    viewController as! AppChildIntroViewController
      var index =   vc.index
      if(index == 0){
          return nil
      }
      index -= 1
      return self.viewControllerAtIndex(index)
  }
  
  func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -&gt; UIViewController? {
      let vc =    viewController as! AppChildIntroViewController
      var index =   vc.index
      index += 1
      if (index == 3) {
          return nil;
      }
      return self.viewControllerAtIndex(index)
  }
  </code></pre>
  
  <p>I was trying to add a push action if <strong>index == 3</strong> but in this case it immediately goes to the app on the last screen</p>