gistfile1.txt

class ForwardSegue: UIStoryboardSegue {
    override func perform() {
        let source = self.sourceViewController as! UIViewController
        let destination = self.destinationViewController as! UIViewController
        let window = UIApplication.sharedApplication().keyWindow!
        
        window.insertSubview(destination.view, aboveSubview: source.view)
        
        destination.animateIn()
        source.animateOut {
        // To fix the issue with unbalanced viewwillappear/disappear calls
            destination.viewWillDisappear(true)
            destination.viewDidDisappear(true)
            
            dispatch_async(dispatch_get_main_queue(), { () -> Void in
                source.presentViewController(destination, animated: false, completion: nil)
            })
        }
    }
}

class BackSegue: UIStoryboardSegue {
    override func perform() {
        let source = self.sourceViewController as! UIViewController
        let destination = self.destinationViewController as! UIViewController
        let window = UIApplication.sharedApplication().keyWindow!
        
        destination.dismissViewControllerAnimated(false, completion: { () -> Void in
            window.insertSubview(source.view, aboveSubview: destination.view)
            
            source.animateOut {
                source.view.removeFromSuperview()
            }
            destination.animateIn()
        })
    }
}