Add child UIViewController to UIView

gistfile1.txt

    func add(viewController: UIViewController, toContainerView containerView: UIView) {
        viewController.view.translatesAutoresizingMaskIntoConstraints = false
        addChildViewController(viewController)
        containerView.addSubview(viewController.view)
        viewController.didMove(toParentViewController: self)
        viewController.view.topAnchor.constraint(equalTo: containerView.topAnchor).isActive = true
        viewController.view.leadingAnchor.constraint(equalTo: containerView.leadingAnchor).isActive = true
        viewController.view.bottomAnchor.constraint(equalTo: containerView.bottomAnchor).isActive = true
        viewController.view.rightAnchor.constraint(equalTo: containerView.rightAnchor).isActive = true
    }