FadeInOutUnwind.swift

import UIKit

class FadeInOutUnwind: UIStoryboardSegue {

  override func perform() {

    let sourceView: UIView = self.source.view as UIView!
    let destinationView: UIView = self.destination.view as UIView!

    sourceView.alpha = 1.0
    destinationView.alpha = 0.0

    let window = UIApplication.shared.keyWindow
    window?.insertSubview(destinationView, aboveSubview: sourceView)

    UIView.animate(withDuration: 0.2, animations: { () -> Void in
      self.source.navigationController?.view.alpha = 0.0
      sourceView.alpha = 0.0
      destinationView.alpha = 1.0
      self.source.navigationController?.view.alpha = 0.0

      }, completion: { (_) -> Void in
        self.source.dismiss(animated: false, completion: nil)
    })
  }

}