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A UIKit custom transition that simulates an elastic drag. Written in Swift.
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ElasticTransition (Swift 3)

Version License Platform

A UIKit custom modal transition that simulates an elastic drag. Written in Swift.


###Thanks to Matt Garnett (@c-o-l-o-r) for converting ElasticTransition to Swift 3

###Also, special thanks to @taglia3 for developing the [Objective-C version] ( Check it out!


  • Xcode 8 or higher
  • iOS 8.0 or higher
  • Swift 3.0



pod "ElasticTransition"



import ElasticTransition
// make your view controller a subclass of ElasticModalViewController
// present it as normal
class YourModalViewController:ElasticModalViewController{ 
  // ... 

class RootViewController:UIViewController{
  // ...
  @IBAction func modalBtnTouched(sender: AnyObject) {
    performSegueWithIdentifier("modalSegueIdentifier", sender: self)

    // or if you want to do customization ---------------------
    let modalViewController = UIStoryboard(name: "Main", bundle: nil).instantiateViewControllerWithIdentifier("modalViewControllerIdentifier") as! YourModalViewController
    // customization:
    modalViewController.modalTransition.edge = .Left
    modalViewController.modalTransition.radiusFactor = 0.3
    // ...

    presentViewController(modalViewController, animated: true, completion: nil)

Attributes you can set:

  // screen edge of the transition
  public var edge:Edge
  // animation stiffness - determines the speed of the animation
  public var stiffness:CGFloat = 0.2
  // animation damping - determines the bounciness of the animation 
  public var damping:CGFloat = 0.2
  // Background view transform
  public var transformType:ElasticTransitionBackgroundTransform = .TranslateMid
  // The curvature of the elastic edge.
  public var radiusFactor:CGFloat = 0.5
   Determines whether or not the view edge will stick to
   the initial position when dragged.
   **Only effective when doing a interactive transition**
  public var sticky:Bool = true
   The initial position of the simulated drag when static animation is performed
   i.e. The static animation will behave like user is dragging from this point
   **Only effective when doing a static transition**
  public var startingPoint:CGPoint?
   The background color of the container when doing the transition
  public var containerColor:UIColor = UIColor(red: 152/255, green: 174/255, blue: 196/255, alpha: 1.0)
   The color of the overlay when doing the transition
  public var overlayColor:UIColor = UIColor(red: 152/255, green: 174/255, blue: 196/255, alpha: 0.5)
   Whether or not to display the shadow. Will decrease performance.
  public var showShadow:Bool = false
   The shadow color of the container when doing the transition
  public var shadowColor:UIColor = UIColor(red: 100/255, green: 122/255, blue: 144/255, alpha: 1.0)
   The shadow radius of the container when doing the transition
  public var shadowRadius:CGFloat = 50

Advance Usage

This work with any view controller.

In prepareForSegue, assign the transition to be the transitioningDelegate of the destinationViewController. Also, dont forget to set the modalPresentationStyle to .Custom

var transition = ElasticTransition()
override func viewDidLoad() {

  // customization
  transition.edge = .Left 
  transition.sticky = false
  // etc
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
  segue.destinationViewController.transitioningDelegate = transition
  segue.destinationViewController.modalPresentationStyle = .Custom

(Optional) In your modal view controller implement the ElasticMenuTransitionDelegate and provide the contentLength

class MenuViewController: UIViewController, ElasticMenuTransitionDelegate {
  var contentLength:CGFloat = 320
  // ...
Interactive transition for modal transition

First, construct a pan gesture recognizer

let panGR = UIPanGestureRecognizer(target: self, action: "handlePan:")

Then implement your gesture handler and fo the following:

func handlePan(pan:UIPanGestureRecognizer){
  if pan.state == .Began{
    // Here, you can do one of two things
    // 1. show a viewcontroller directly
    let nextViewController = // construct your VC ...
    transition.startInteractiveTransition(self, toViewController: nextViewController, gestureRecognizer: pan)
    // 2. perform a segue
    transition.startInteractiveTransition(self, segueIdentifier: "menu", gestureRecognizer: pan)
    transition.updateInteractiveTransition(gestureRecognizer: pan)
Interactive transition for dismissing the modal
  1. Implement ElasticMenuTransitionDelegate in your modal view controller and set
  var dismissByBackgroundTouch = true
  var dismissByBackgroundDrag = true
  var dismissByForegroundDrag = true
  1. Or use your own panGestureRecognizer and call dissmissInteractiveTransition in your handler
func handlePan(pan:UIPanGestureRecognizer){
  if pan.state == .Began{
    transition.dissmissInteractiveTransition(self, gestureRecognizer: pan, completion: nil)
    transition.updateInteractiveTransition(gestureRecognizer: pan)


Luke Zhao,


ElasticTransition is available under the MIT license. See the LICENSE file for more info.

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