Warning: Attempt to present error when trying to present UIAlertController on Custom

Question

Warning: Attempt to present on whose view is not in the window hierarchy!

I have a custom presented view controller and would like to present UIAlertController on top of it. When presenting without custom transition everything works fine.

Tried adding definesPresentationContext = true without luck

Maybe my custom transition should include something like addChildViewController() ?

First VC

let adVC = AdViewController(with: adView)
adVC.setupAd(with: index)
let adNav = UINavigationController(rootViewController: adVC)
adNav.modalPresentationStyle = .custom
adNav.transitioningDelegate = adVC.adCustomTransition
self.present(adNav, animated: true, completion: nil)

AdViewController

class AdViewController: UIViewController {

    var adCustomTransition = AdCustomTransition()

    override func viewDidLoad() {
    super.viewDidLoad()

        definesPresentationContext = true;
        submitButton.addTarget(self, action: #selector(presentAlert), for: .touchUpInside)

    }

    func presentAlert() {
        DispatchQueue.main.async {
            let alertVC = UIAlertController(title: "Alert!", message: "test alert message", preferredStyle: .alert)
            alertVC.view.tintColor = .main
            alertVC.addAction(UIAlertAction(title: "Ok", style: .default, handler: nil))
            self.present(alertVC, animated: true, completion: nil)
        }
    }
}




    class AdCustomTransition : NSObject, UIViewControllerTransitioningDelegate {


        func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
            return AdAnimationController(withDuration: 0.4, forTransitionType: .present)
        }

        func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
            return AdAnimationController(withDuration: 0.4, forTransitionType: .dismiss)
        }
    }

    class AdAnimationController: NSObject, UIViewControllerAnimatedTransitioning {

        enum TransitionType {
            case present, dismiss
        }

        var duration: TimeInterval
        var isPresenting: Bool

        init(withDuration duration: TimeInterval, forTransitionType type: TransitionType) {
            self.duration = duration
            self.isPresenting = type == .present
            super.init()
        }



        func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
            return self.duration
        }

        func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {

            let containerView = transitionContext.containerView
            let toFrame = transitionContext.finalFrame(for: transitionContext.viewController(forKey: .to)!)

            if isPresenting == true {
                let toVC = (transitionContext.viewController(forKey: .to) as! MainNavigationController).viewControllers.first as! AdViewController

                containerView.addSubview(toVC.view)
                containerView.layoutIfNeeded()

                let bottomHeight = toVC.getSafeBottomHeight()
                let offset = toVC.containerView.bounds.height - 120 - bottomHeight

                toVC.containerView.transform = CGAffineTransform(translationX: 0, y: offset)

                UIView.animate(withDuration: self.duration, delay: 0, usingSpringWithDamping: 5.4, initialSpringVelocity: 0.8, options: .curveEaseInOut, animations: {
                    toVC.containerView.transform = CGAffineTransform(translationX: 0, y: -1 * bottomHeight)
                }, completion: { (_) in
                    toVC.view.frame = toFrame
                    transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
                })

            } else {

                let fromVC = (transitionContext.viewController(forKey: .from) as! MainNavigationController).viewControllers.first as! AdViewController
                let toVC = transitionContext.viewController(forKey: .to)!

                containerView.addSubview(toVC.view)
                containerView.addSubview(fromVC.view)

                containerView.layoutIfNeeded()

                let bottomHeight = fromVC.getSafeBottomHeight()

                let offset = fromVC.containerView.bounds.height - 110 - bottomHeight
                fromVC.containerView.transform = .identity

                UIView.animate(withDuration: self.duration, delay: 0, usingSpringWithDamping: 5.7, initialSpringVelocity: 0.8, options: .curveEaseInOut, animations: {
                    fromVC.containerView.transform = CGAffineTransform(translationX: 0, y: offset)
                }, completion: { (_) in
                    toVC.view.frame = toFrame
                    UIApplication.shared.keyWindow?.addSubview(toVC.view)
                    transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
                })
            }
        }
}