Snapchat-like swipe navigation between views in Xcode 6 and Swift)

Question

I\'ve been trying to implement swipe navigation between View Controllers in my app using the Swipe Gesture Recognizer and embeded Navigation Controller, but it doesn\'t look eve

Answer 1

I'm not fond of the version given by lbrendanl because it does not use constraints. We can not custom it like we want. Here is the same version but with constraints :

scrollView is an IBOutlet pined to the controller with 4 constraints with a constant to 0 at each sides to the controller's view.

contentView is also an IBOutlet added as subview of scrollView pined to the scrollView with 4 constraints with a constant to 0 at each sides. It also has an equal height constraint and a width equal constraint. The width equal constraint is removed at runtime and only serves to calm down IB. This view represents the contentView of the scrollView.

UPDATE iOS 9

 func setupDetailViewControllers() {
    var previousController: UIViewController?
    for controller in self.controllers {
        addChildViewController(controller)
        addControllerInContentView(controller, previousController: previousController)
        controller.didMoveToParentViewController(self)
        previousController = controller
    }
}

func addControllerInContentView(controller: UIViewController, previousController: UIViewController?) {
    contentView.addSubview(controller.view)
    controller.view.translatesAutoresizingMaskIntoConstraints = false

    // top
    controller.view.topAnchor.constraintEqualToAnchor(contentView.topAnchor).active = true

    // bottom
    controller.view.bottomAnchor.constraintEqualToAnchor(contentView.bottomAnchor).active = true

    // trailing
    trailingContentViewConstraint?.active = false
    trailingContentViewConstraint = controller.view.trailingAnchor.constraintEqualToAnchor(contentView.trailingAnchor)
    trailingContentViewConstraint?.active = true

    // leading
    let leadingAnchor = previousController?.view.trailingAnchor ?? contentView.leadingAnchor
    controller.view.leadingAnchor.constraintEqualToAnchor(leadingAnchor).active = true

    // width
    controller.view.widthAnchor.constraintEqualToAnchor(scrollView.widthAnchor).active = true
}

PREVIOUS ANSWER

    class ContainerViewController: UIViewController {

    @IBOutlet var scrollView: UIScrollView!
    @IBOutlet var contentView: UIView!

    // A strong reference to the width contraint of the contentView
    var contentViewConstraint: NSLayoutConstraint!

    // A computed version of this reference
    var computedContentViewConstraint: NSLayoutConstraint {
        return NSLayoutConstraint(item: contentView, attribute: NSLayoutAttribute.Width, relatedBy: NSLayoutRelation.Equal, toItem: scrollView, attribute: .Width, multiplier: CGFloat(controllers.count + 1), constant: 0)
    }

    // The list of controllers currently present in the scrollView
    var controllers = [UIViewController]()

    override func viewDidLoad() {
        super.viewDidLoad()

        initScrollView()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()

    }

    func initScrollView(){
        contentView.setTranslatesAutoresizingMaskIntoConstraints(false)

        contentViewConstraint = computedContentViewConstraint
        view.addConstraint(contentViewConstraint)

        // Adding all the controllers you want in the scrollView
        let controller1 = storyboard!.instantiateViewControllerWithIdentifier("AStoryboardID") as! AnUIControllerViewSubclass
        addToScrollViewNewController(controller)
        let controller2 = storyboard!.instantiateViewControllerWithIdentifier("AnotherStoryboardID") as! AnotherUIControllerViewSubclass
        addToScrollViewNewController(controller2)
    }

    // The main method, adds the controller in the scrollView at the left of the previous controller added
    func addToScrollViewNewController(controller: UIViewController) {
        self.addChildViewController(controller)

        contentView.addSubview(controller.view)

        controller.view.setTranslatesAutoresizingMaskIntoConstraints(false)

        // Setting all the constraints 
        let bottomConstraint = NSLayoutConstraint(item: contentView, attribute: .Bottom, relatedBy: .Equal, toItem: controller.view, attribute: .Bottom, multiplier: 1.0, constant: 0)

        let topConstraint = NSLayoutConstraint(item: contentView, attribute: .Top, relatedBy: .Equal, toItem: controller.view, attribute: .Top, multiplier: 1.0, constant: 0)

        let widthConstraint = NSLayoutConstraint(item: controller.view, attribute: .Width, relatedBy: .Equal, toItem: scrollView, attribute: .Width, multiplier: 1.0, constant: 0)

        var trailingConstraint: NSLayoutConstraint!
        if controllers.isEmpty {
            // Since it's the first one, the trailing constraint is from the controller view to the contentView
            trailingConstraint = NSLayoutConstraint(item: contentView, attribute: .Trailing, relatedBy: .Equal, toItem: controller.view, attribute: .Trailing, multiplier: 1.0, constant: 0)
        }
        else {
            trailingConstraint = NSLayoutConstraint(item: controllers.last!.view, attribute: .Leading, relatedBy: .Equal, toItem: controller.view, attribute: .Trailing, multiplier: 1.0, constant: 0)
        }

        // Setting the new width constraint of the contentView
        view.removeConstraint(contentViewConstraint)
        contentViewConstraint = computedContentViewConstraint

        // Adding all the constraints to the view hierarchy
        view.addConstraint(contentViewConstraint)
        contentView.addConstraints([bottomConstraint, topConstraint, trailingConstraint])
        scrollView.addConstraints([widthConstraint])

        controller.didMoveToParentViewController(self)

        // Finally adding the controller in the list of controllers
        controllers.append(controller)
    }  
}

I've used the lbrendanl's version in the past. Now I prefer this one. Let me know what you think of it.