Custom Transition

CustomPresentation.swift

class CustomPresentation: UIPresentationController {
    override var frameOfPresentedViewInContainerView: CGRect {
        return CGRect(x: 0, y: containerView!.bounds.height / 2, width: containerView!.bounds.width, height: containerView!.bounds.height / 2)
    }
    
    override func containerViewWillLayoutSubviews() {
        presentedView?.center = .zero
        presentedView?.frame = frameOfPresentedViewInContainerView
    }
}

CustomTransition+UIViewControllerTransitioningDelegate.swift

extension CustomTransition: UIViewControllerTransitioningDelegate {
    func presentationController(forPresented presented: UIViewController, presenting: UIViewController?, source: UIViewController) -> UIPresentationController? {
        return CustomPresentation(presentedViewController: presented, presenting: presenting)
    }
    
    func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        state = .present
        return self
    }
    
    func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        state = .dismiss
        return self
    }
    
    func interactionControllerForDismissal(using animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {
        let interactor = Interactor()
        return interactor.hasStarted ? interactor : nil
    }
}

CustomTransition.swift

class CustomTransition: NSObject, UIViewControllerAnimatedTransitioning {
    enum TransitionState {
        case present
        case dismiss
    }
    
    private var state: TransitionState = .present
    
    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 0.3
    }
    
    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        let container = transitionContext.containerView
        let duration = transitionDuration(using: transitionContext)
        switch state {
        case .present:
            present(duration: duration, container: container, transitionContext: transitionContext)
        case .dismiss:
            dismiss(duration: duration, container: container, transitionContext: transitionContext)
        }
    }
    
    private func present(duration: TimeInterval, container: UIView, transitionContext: UIViewControllerContextTransitioning) {
        let from = transitionContext.viewController(forKey: .from)!
        let to = transitionContext.viewController(forKey: .to)!
        let toFinalFrame = transitionContext.finalFrame(for: to)
        container.addSubview(from.view)
        container.insertSubview(to.view, aboveSubview: from.view)
        to.view.frame = CGRect(x: 0, y: toFinalFrame.height, width: toFinalFrame.width, height: toFinalFrame.height)
        UIView.animate(withDuration: duration, animations: {
            to.view.frame = CGRect(x: 0, y: 0, width: toFinalFrame.width, height: toFinalFrame.height)
        }) { (_) in
            transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
        }
    }
    
    private func dismiss(duration: TimeInterval, container: UIView, transitionContext: UIViewControllerContextTransitioning) {
        let from = transitionContext.viewController(forKey: .from)!
        let fromFinalFrame = transitionContext.finalFrame(for: from)
        UIView.animate(withDuration: duration, animations: {
            from.view.frame = CGRect(x: 0, y: container.bounds.height, width: fromFinalFrame.width, height: fromFinalFrame.height)
        }) { (_) in
            transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
        }
    }
}

Interactor.swift

class Interactor: UIPercentDrivenInteractiveTransition {
    var hasStarted = false
    var shouldFinish = false
}