Handling container views in code

ParentViewController.swift

// thanks dude
// https://medium.com/@dushyant_db/setting-up-a-container-view-using-interface-builder-and-via-code-7ac1a7f0a0d6 

override func viewDidLoad() {
    super.viewDidLoad()
    
    guard let childVC = self.storyboard?.instantiateViewController(withIdentifier: "ChildViewController") as? ChildViewController else {
      return
    }
addChildViewController(childVC)
    //Or, you could add auto layout constraint instead of relying on AutoResizing contraints
    childVC.view.autoresizingMask = [.flexibleHeight, .flexibleWidth]
    childVC.view.frame = containerView.bounds
    
    containerView.addSubview(childVC.view)
    childVC.didMove(toParentViewController: self)
    
    //Some property on ChildVC that needs to be set
    childVC.dataSource = self
  }
}