Left/right segues, Swift 3

gistfile1.txt

extension UIStoryboardSegue {
    func presentWith(direction: SegueTransitionDirection) {
        let offset: CGFloat
        switch direction {
        case .right:
            offset = -1
        case .left:
            offset = 1
        }
        let firstClassView = self.source.view
        let secondClassView = self.destination.view
        secondClassView?.isUserInteractionEnabled = false

        let screenWidth = UIScreen.main.bounds.size.width
        let screenHeight = UIScreen.main.bounds.size.height

        secondClassView?.frame = CGRect(x: -1 * offset * screenWidth, y: 0, width: screenWidth, height: screenHeight)

        if let window = UIApplication.shared.keyWindow {

            window.insertSubview(secondClassView!, aboveSubview: firstClassView!)

            UIView.animate(withDuration: 0.2, animations: { () -> Void in

                firstClassView?.frame = (firstClassView?.frame.offsetBy(dx: offset * screenWidth, dy: 0))!
                secondClassView?.frame = (secondClassView?.frame.offsetBy(dx: offset * screenWidth, dy: 0))!

            }, completion: {(Finished) -> Void in

                self.source.navigationController?.present(self.destination,
                                                          animated: false,
                                                          completion: { _ in return
                    secondClassView?.isUserInteractionEnabled = true
                })
                
            }) 
            
        }
    }

    func unwindWith(direction: SegueTransitionDirection) {
        let sourceView = self.source.view as UIView!
        let destinationView = self.destination.view as UIView!
        let window = UIApplication.shared.delegate?.window!

//        window?.insertSubview(destinationView!, belowSubview: sourceView!)

        destinationView?.center = CGPoint(x: (sourceView?.center.x)!, y: (sourceView?.center.y)! + (destinationView?.center.y)!)

        UIView.animate(withDuration: 0.4,
                       animations: {
                        destinationView?.center = CGPoint(x: (sourceView?.center.x)!, y: (sourceView?.center.y)!)
                        sourceView?.center = CGPoint(x: (sourceView?.center.x)!, y: 0 - 2 * (destinationView?.center.y)!)
        }, completion: {
            (value: Bool) in
            //4. dismiss

            let sourceNavCont = self.source.navigationController?.viewControllers
            var strings1: [String] = []
            for vc in sourceNavCont! {
                strings1.append(String(describing: vc))
            }
            let destNavCont = self.destination.navigationController?.viewControllers
            var strings2: [String] = []
            for vc in destNavCont! {
                strings2.append(String(describing: vc))
            }
            dump(strings1)
            dump(strings2)

            self.source.navigationController?.view.removeFromSuperview()
            if let navController = self.destination.navigationController {
                let appDelegate = UIApplication.shared.delegate as! AppDelegate
                appDelegate.window?.rootViewController = navController
            }
        })
    }
}

enum SegueTransitionDirection {
    case left
    case right
}