Segue from Right (Slide the next controllers view in from right to left (and back))

1.UIStoryboardSegueFromRight.swift

import UIKit

class UIStoryboardSegueFromRight: UIStoryboardSegue {
    
    override func perform()
    {
        let src = self.sourceViewController as UIViewController
        let dst = self.destinationViewController as UIViewController
        
        src.view.superview?.insertSubview(dst.view, aboveSubview: src.view)
        dst.view.transform = CGAffineTransformMakeTranslation(src.view.frame.size.width, 0)

        UIView.animateWithDuration(0.25,
            delay: 0.0,
            options: UIViewAnimationOptions.CurveEaseInOut,
            animations: {
                dst.view.transform = CGAffineTransformMakeTranslation(0, 0)
            },
            completion: { finished in
                src.presentViewController(dst, animated: false, completion: nil)
            }
        )
    }
}

class UIStoryboardUnwindSegueFromRight: UIStoryboardSegue {
    
    override func perform()
    {
        let src = self.sourceViewController as UIViewController
        let dst = self.destinationViewController as UIViewController
        
        src.view.superview?.insertSubview(dst.view, belowSubview: src.view)
        src.view.transform = CGAffineTransformMakeTranslation(0, 0)
        
        UIView.animateWithDuration(0.25,
            delay: 0.0,
            options: UIViewAnimationOptions.CurveEaseInOut,
            animations: {
                src.view.transform = CGAffineTransformMakeTranslation(src.view.frame.size.width, 0)
            },
            completion: { finished in
                src.dismissViewControllerAnimated(false, completion: nil)
            }
        )
    }
}

2.Instructions.md

Assign the class UIStoryboardSegueFromRight to the custom segue in the storyboard.

To create an Unwind Segue, you'll need the code below in the first controller. You'll use the segueToMe to connect to the Exit in the second controller. Give that Unwind segue the identifier e.g. "returnToMainViewController".

3.MainViewController.swift

    
    @IBAction func segueToMe(segue: UIStoryboardSegue) {
        // segue back
    }

    override func segueForUnwindingToViewController(toViewController: UIViewController, fromViewController: UIViewController, identifier: String?) -> UIStoryboardSegue {

        if let id = identifier {
            if id == "returnToMainViewController" {
                let unwindSegue = UIStoryboardUnwindSegueFromRight(identifier: id, source: fromViewController, destination: toViewController)
                return unwindSegue
            }        
        }
        
        return super.segueForUnwindingToViewController(toViewController, fromViewController: fromViewController, identifier: identifier)
    }
    

Here is the code updated to Swift 4.2

This goes in a separate UIStoryboardSegueExtensions swift file

import UIKit

class UIStoryboardSegueFromRight: UIStoryboardSegue {

override func perform()
{
    let src = self.source as UIViewController
    let dst = self.destination as UIViewController
    
    src.view.superview?.insertSubview(dst.view, aboveSubview: src.view)
    dst.view.transform = CGAffineTransform(translationX: src.view.frame.size.width, y: 0)
    
    UIView.animate(withDuration: 0.25,
                               delay: 0.0,
                               options: [.curveEaseIn, .curveEaseOut],
                               animations: {
                                dst.view.transform = CGAffineTransform(translationX: 0, y: 0)
    },
                               completion: { finished in
                                src.present(dst, animated: false, completion: nil)
    }
    )
}

}

class UIStoryboardUnwindSegueFromRight: UIStoryboardSegue {

override func perform()
{
    let src = self.source as UIViewController
    let dst = self.destination as UIViewController
    
    src.view.superview?.insertSubview(dst.view, belowSubview: src.view)
    src.view.transform = CGAffineTransform(translationX: 0, y: 0)
    
    UIView.animate(withDuration: 0.25,
                               delay: 0.0,
                               options: [.curveEaseIn, .curveEaseOut],
                               animations: {
                                src.view.transform = CGAffineTransform(translationX: src.view.frame.size.width, y: 0)
    },
                               completion: { finished in
                                src.dismiss(animated: false, completion: nil)
    }
    )
}

}

And this is the revised code for your source view controller

override func segueForUnwinding(to toViewController: UIViewController, from fromViewController: UIViewController, identifier: String?) -> UIStoryboardSegue {

    if let id = identifier {
        if id == "returnToMainViewController" {
            let unwindSegue = UIStoryboardUnwindSegueFromRight(identifier: id, source: fromViewController, destination: toViewController)
            return unwindSegue
        }
    }
    
    return super.segueForUnwinding(to: toViewController, from: fromViewController, identifier: identifier)!
}

@IBAction func segueToMe(segue: UIStoryboardSegue) {
    let controller = segue.source as! ##SecondViewController##
} 

Tested and works

This keeps crashing for me on the UIStoryboardSegueFromRight function.

completion: { finished in
                                src.present(dst, animated: false, completion: nil)
    }

Sometimes it works and sometimes it crashes with an unspecific error.

This keeps crashing for me on the UIStoryboardSegueFromRight function.

completion: { finished in
                                src.present(dst, animated: false, completion: nil)
    }

Sometimes it works and sometimes it crashes with an unspecific error.

The same happens for me. What did you end up doing matt?

Seems not a solution anymore in 2023:

iOS15, > Swift 5.5, code always crashes on the src.present command.