title: Cannot add viewcontroller´s frame to a scrollview in another viewcontroller
body: <p>I want to add a swipe function to my app and swipe between viewcontrollers as in this tutorial: <a href="https://www.youtube.com/watch?v=3jAlg5BnYUU" rel="nofollow">https://www.youtube.com/watch?v=3jAlg5BnYUU</a>
  The source code for the tutorial is here: <a href="https://www.veasoftware.com/posts/swipe-navigation-in-swift-xcode-7-ios-9-tutorial" rel="nofollow">https://www.veasoftware.com/posts/swipe-navigation-in-swift-xcode-7-ios-9-tutorial</a></p>
  
  <p>In that guide they are using <code>nib/xib</code> files that they create together with the corresponding viewcontrollers that they then use to call for in their ViewController´s constructors. </p>
  
  <p>I have done exact the same and it is wokring as in the tutorial. But I also want use a ViewController that not has a <code>xib</code> file because it is on my storyboard. That viewcontroller is called <code>ViewController2</code> in my code below and it is the only that does not appear in the scrollview when I swipe. The other two do because I call for the <code>xibName</code> in the constructor call but ViewController2 does not have a <code>xib</code> file since it is on my storyboard. </p>
  
  <p>So how can I add it to the scrollview so it appears when I swipe?</p>
  
  <pre><code>@IBOutlet weak var scrollView: UIScrollView!
  
  override func viewDidLoad() {
      super.viewDidLoad()
  
      let vc0 = ViewController0(nibName: "ViewController0", bundle: nil)
  
      self.addChildViewController(vc0)
      self.scrollView.addSubview(vc0.view)
      vc0.didMoveToParentViewController(self)
  
      let vc1 = ViewController1(nibName: "ViewController1", bundle: nil)
  
      var frame1 = vc1.view.frame
      frame1.origin.x = self.view.frame.size.width
      vc1.view.frame = frame1
  
      self.addChildViewController(vc1)
      self.scrollView.addSubview(vc1.view)
      vc1.didMoveToParentViewController(self)
  
      let vc2 = ViewController2()
  
      var frame2 = vc2.view.frame
      frame2.origin.x = self.view.frame.size.width
      vc2.view.frame = frame2
  
      self.addChildViewController(vc2)
      self.scrollView.addSubview(vc2.view)
      vc2.didMoveToParentViewController(self)
  
      self.scrollView.contentSize = CGSizeMake(self.view.frame.size.width * 3, self.view.frame.size.height - 66);
  }
  </code></pre>