title: Empty TableView when embedded as a child view controller into a container view
body: <p>I have a TableViewController as a child view controller of a container view. For some reason, the table view controller does not show any of its rows. It shows its background color, but the information is absent.
  Is this natural?
  Here is the code:</p>
  
  <pre><code>override func viewDidLoad() {
      super.viewDidLoad()
  
      view.addSubview(topBar)
      topBar.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
      topBar.widthAnchor.constraint(equalTo: view.widthAnchor).isActive = true
      topBar.heightAnchor.constraint(equalToConstant: 80).isActive = true
      topBar.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
  
      view.addSubview(containerView)
      containerView.topAnchor.constraint(equalTo: topBar.bottomAnchor).isActive = true
      containerView.widthAnchor.constraint(equalTo: view.widthAnchor).isActive = true
      containerView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
      containerView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
  
      topBar.addSubview(subjects)
      subjects.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
      subjects.topAnchor.constraint(equalTo: view.topAnchor, constant: 30).isActive = true
  
      topBar.addSubview(backButton)
  
      backButton.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 20).isActive = true
      backButton.topAnchor.constraint(equalTo: view.topAnchor, constant: 30).isActive = true
  
      let subjectsView = SubjectsTableViewController().view!
  
      subjectsView.translatesAutoresizingMaskIntoConstraints = false
  
      containerView.addSubview(subjectsView)
  
      subjectsView.topAnchor.constraint(equalTo: containerView.topAnchor).isActive = true
      subjectsView.bottomAnchor.constraint(equalTo: containerView.bottomAnchor).isActive = true
      subjectsView.leftAnchor.constraint(equalTo: containerView.leftAnchor).isActive = true
      subjectsView.rightAnchor.constraint(equalTo: containerView.rightAnchor).isActive = true
  }
  </code></pre>