为什么我的视图控制器没有被释放？

Question

我正在使用UIPercentDrivenInteractiveTransition，当我将它与UIPanGestureRecognizer对象结合使用时，它可以正常工作。但是，当我关闭我的视图控制器（在didPan函数中）时，相关的内存不会被释放。你能解释一下为什么吗？我的代码如下：

class SecondViewController: UIViewController {

    var panGestureRecognizer: UIPanGestureRecognizer!
    var customInteractionAnimation = CustomInteractiveDismissAnimation()

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = UIColor.clear
        let myView = UIView(frame: CGRect(x: 30, y: 100, width: view.bounds.size.width - 60, height: 200))
        myView.layer.cornerRadius = 10
        myView.backgroundColor = UIColor.orange
        panGestureRecognizer = UIPanGestureRecognizer(target: self, action: #selector(didPan))
        view.addGestureRecognizer(panGestureRecognizer)
        view.addSubview(myView)
    }


    required init?(coder aDecoder: NSCoder){
        super.init(coder: aDecoder)
        self.modalPresentationStyle = UIModalPresentationStyle.custom
        transitioningDelegate = self

    }

    func didPan(){

        switch panGestureRecognizer.state{
        case .began:
            customInteractionAnimation.interactive = true
            print("Did PAN")
            //performSegue(withIdentifier: "mySegue2", sender: self)
            dismiss(animated: true, completion: nil)
        default:
            customInteractionAnimation.handelPan(recognizer: panGestureRecognizer!)
        }
    }

    @IBAction func goToFirstViewController(_ segue: UIStoryboardSegue){

    }

    deinit {
        print("Second view contoller was deallocated!")
    }

}

extension SecondViewController: UIViewControllerTransitioningDelegate{

    func presentationController(forPresented presented: UIViewController, presenting: UIViewController?, source: UIViewController) -> UIPresentationController? {
        return CustomUIPresentationController(presentedViewController: presented, presenting: presenting)
    }
    func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return CustomAnimationController()
    }


    func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return CustomDismissAnimation()
    }

   func interactionControllerForDismissal(using animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {

        if !customInteractionAnimation.interactive{
            return nil
        } else {
            print("Returned Interaction animation object")
            return customInteractionAnimation
        }
    }
}

P.S。对不起凌乱的代码感到抱歉。

编辑：这是我的演示控制器

class CustomUIPresentationController: UIPresentationController {

    lazy var gradientView = GradientDimmingView(frame: CGRect.zero)
    override func presentationTransitionWillBegin() {
        gradientView.frame = containerView!.bounds
        containerView?.insertSubview(gradientView, at: 0)
        gradientView.alpha = 0
        if let coordinator = presentedViewController.transitionCoordinator{
            coordinator.animate(alongsideTransition: {_ in
                self.gradientView.alpha = 1
                }, completion: nil)
        }
    }

    override var shouldRemovePresentersView: Bool {
        return false
    }

}