custom_segue_swift3_perform.swift

override func perform() {

        //set the ViewControllers for the animation

        let sourceView = self.source.view as UIView!
        let destinationView = self.destination.view as UIView!
        
        
        let window = UIApplication.shared.delegate?.window!
        //set the destination View center
        destinationView?.center = CGPoint(x: (sourceView?.center.x)!, y: (sourceView?.center.y)! - (destinationView?.center.y)!)
        
        // the Views must be in the Window hierarchy, so insert as a subview the destionation above the source
        window?.insertSubview(destinationView!, aboveSubview: sourceView!)
        
        //create UIAnimation- change the views's position when present it
        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
                elf.source.navigationController?.pushViewController(self.destination, animated: false)
 
                
})