title: Why can't I stop the page-curl animation in UIPageViewController
body: <p>I trying to use <code>UIPageViewController</code> to move between controllers. Everything is working fine, but the only issue is that I am changing the transition style in the storyboard from page-curl to scroll. but it is not working. When I run the app and move between controllers, the animation is page-curl !!! </p>
  
  <p>my code is simple, you can check it:</p>
  
  <pre><code>override func viewDidLoad() {
          super.viewDidLoad()             
          let firstViewController = orderedViewControllers[1]
          setViewControllers([firstViewController],
                                 direction: .forward,
                                 animated: false,
                                 completion: nil) 
          self.delegate = self
          self.dataSource = self 
      }
  
  func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -&gt; UIViewController? {
          guard let viewControllerIndex = orderedViewControllers.index(of: viewController) else {
              return nil
          }
  
          let previousIndex = viewControllerIndex - 1
  
          // User is on the first view controller and swiped left to loop to
          // the last view controller.
          guard previousIndex &gt;= 0 else {
               return nil
          }
  
          guard orderedViewControllers.count &gt; previousIndex else {
              return nil
          }
          return orderedViewControllers[previousIndex]
      }
  
      func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -&gt; UIViewController? {
          guard let viewControllerIndex = orderedViewControllers.index(of: viewController) else {
              return nil
          }
  
          let nextIndex = viewControllerIndex + 1
          let orderedViewControllersCount = orderedViewControllers.count
  
          // User is on the last view controller and swiped right to loop to
          // the first view controller.
          guard orderedViewControllersCount != nextIndex else {
               return nil
          }
  
          guard orderedViewControllersCount &gt; nextIndex else {
              return nil
          }
          return orderedViewControllers[nextIndex]
      }
      ```
  </code></pre>