TransitionAnimator.swift

import UIKit
import PlaygroundSupport

class FirstTable: UITableViewController, UIViewControllerTransitioningDelegate {
    
    lazy var animator = TransitionAnimator()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        tableView.register(UITableViewCell.self, forCellReuseIdentifier: "reuseID")
    }
    
    override func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }
    
    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 20
    }
    
    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "reuseID", for: indexPath)
        cell.textLabel?.text = "Press Me"
        return cell
    }
    
    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        let second = SecondTable(style: UITableViewStyle.grouped)
        second.transitioningDelegate = self
        present(second, animated: true, completion: nil)
    }
    
    func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        animator.isPresenting = true
        return animator
    }
    
    func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        animator.isPresenting = false
        return animator
    }
}


class TransitionAnimator: NSObject, UIViewControllerAnimatedTransitioning {
    
    let duration: Double = 1
    
    var isPresenting = true
    
    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return duration
    }
    
    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        if isPresenting {
            animatePresentation(using: transitionContext)
        } else {
            animateDismissal(using: transitionContext)
        }
    }
    
    func animatePresentation(using transitionContext: UIViewControllerContextTransitioning){
        guard let toVC = transitionContext.viewController(forKey: .to) as? UITableViewController else {
            return
        }
        
        let yTransform: CGFloat = 10
        
        for cell in toVC.tableView.visibleCells{
            cell.alpha = 0
            cell.transform = cell.transform.translatedBy(x: 0, y: yTransform)
        }
        
        toVC.view.alpha = 0.8
        
        let containerView = transitionContext.containerView
        containerView.addSubview(toVC.view)
        
        
        let duration = transitionDuration(using: transitionContext)
        
        let count = Double(toVC.tableView.indexPathsForVisibleRows?.count ?? 1)
        
        let totalDelay = 0.01 * count
        
        let individualDelay = totalDelay / count
        
        let leftOverTime = duration - totalDelay
        
        let individualDuration = leftOverTime / count
        
        for (offset, cell) in toVC.tableView.visibleCells
            .reversed()
            .enumerated() {
            UIView.animate(withDuration: individualDuration, delay: individualDelay * Double(offset), usingSpringWithDamping: 0.2, initialSpringVelocity: 10, options: [], animations: {
                cell.alpha = 1
                cell.transform = .identity
            }, completion: nil)
        }
        
        UIView.animate(withDuration: duration, animations: {
            toVC.view.alpha = 1
        }, completion: { finished in
            let cancelled = transitionContext.transitionWasCancelled
            transitionContext.completeTransition(!cancelled)
        })
    }
 
    func animateDismissal(using transitionContext: UIViewControllerContextTransitioning){
        guard let fromVC = transitionContext.viewController(forKey: .from) as? UITableViewController else {
            return
        }
        
        
        let containerView = transitionContext.containerView
        containerView.addSubview(fromVC.view)
    
        let duration = transitionDuration(using: transitionContext)
        
        let count = Double(fromVC.tableView.indexPathsForVisibleRows?.count ?? 1)
        
        let totalDelay = 0.01 * count
        
        let individualDelay = totalDelay / count
        
        let leftOverTime = duration - totalDelay
        
        let individualDuration = leftOverTime / count
        
        for (offset, cell) in fromVC.tableView.visibleCells
            .reversed()
            .enumerated() {
                UIView.animate(withDuration: individualDuration, delay: individualDelay * Double(offset), usingSpringWithDamping: 0.2, initialSpringVelocity: 10, options: [], animations: {
                    cell.alpha = 1
                    cell.transform = cell.transform.translatedBy(x: 0, y: 100)
                }, completion: nil)
        }
        
        UIView.animate(withDuration: duration, animations: {
            fromVC.view.alpha = 0
        }, completion: { finished in
            let cancelled = transitionContext.transitionWasCancelled
            transitionContext.completeTransition(!cancelled)
        })
    }
}


class SecondTable: UITableViewController {
   
    override func viewDidLoad() {
        super.viewDidLoad()
        tableView.register(UITableViewCell.self, forCellReuseIdentifier: "reuseID")
        automaticallyAdjustsScrollViewInsets = false
    }
    
    override func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }
    
    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 20
    }
    
    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "reuseID", for: indexPath)
        cell.textLabel?.text  = "WWDC"
        return cell
    }
    
    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        dismiss(animated: true, completion: nil)
    }
}


PlaygroundPage.current.liveView = FirstTable(style: .plain)