title: Passing data from API call among parent/child VC relationships
body: <p>I am working on a UIPageViewController embedded in a container view and am struggling with passing information from the parent VC to its corresponding child VC's after making an API call (Parent VC → ContainerView → UIPageVC → UITableVC &amp; VC with an UIImageView). Am I implementing this correctly? It doesn't seem like the data is passing properly.</p>
  <p>It's also worth noting that the app crashes with the following error when including performSegue(withIdentifier: , sender:) in the parent's API call: &quot;There are unexpected subviews in the container view. Perhaps the embed segue has already fired once or a subview was added programmatically?&quot;</p>
  <p>In the parent VC:</p>
  <pre><code>    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
      if segue.identifier == &quot;ToPageVC&quot; {
          let destVC = segue.destination as! MixPageViewController
          destVC.mix = self.mix
      }
  }
  </code></pre>
  <p>Parent VC's API call:</p>
  <pre><code>    private func configureForMix(mix: Mix) {
          self.performSegue(withIdentifier: &quot;ToPageVC&quot;, sender: self)
      }
  </code></pre>
  <p>UIPageVC:</p>
  <pre><code>var mix: Mix?
  
  override func viewDidLoad() {
      super.viewDidLoad()
      
      self.delegate = self
      self.dataSource = self
      let tableViewVC = MixTableViewController()
      let mixPicVC: MixPicViewController! = storyboard?.instantiateViewController(withIdentifier: &quot;MixPicVC&quot;) as? MixPicViewController
      tableViewVC.mix = self.mix
      mixPicVC.mixPicURL = self.mix?.imageURL
  }
  </code></pre>