PresentingView.swift

final class ViewController: UIViewController, UIViewControllerTransitioningDelegate {
    @objc func showView() {
        let presentedViewController = PresentedViewController()
        presentedViewController.modalPresentationStyle = .custom
        presentedViewController.transitioningDelegate = self
        present(presentedViewController, animated: true, completion: nil)
    }

    private let transition = CustomTransition()
    
    func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return transition
    }
}