ios swift custom transition to darken fromViewController

Question

I want to present my view controller with a custom transition so the fromViewController will be darkened as if presenting a AlertViewController. I have created my customTransition manager:

func animateTransition(transitionContext: UIViewControllerContextTransitioning) {
    let container = transitionContext.containerView()
    let fromView = transitionContext.viewForKey(UITransitionContextFromViewKey)!
    let toView = transitionContext.viewForKey(UITransitionContextToViewKey)!

    let fadeRect = CGRectMake(0, 0, fromView.frame.size.width, fromView.frame.size.height)
    let fadeView = UIView(frame: fadeRect)

    if  (self.presenting == true){

        fadeView.backgroundColor = UIColor.blackColor()
        fadeView.alpha = 0

        fromView.addSubview(fadeView)
        container.insertSubview(fadeView, aboveSubview: fromView)
    } else {

//             adding subviews to container
    }

    let duration = self.transitionDuration(transitionContext)

    UIView.animateWithDuration(duration, animations: { () -> Void in

        if  (self.presenting == true){
            fadeView.alpha = 0.5
        } else {

        }
        }) { (Bool) -> Void in
            if self.presenting{
                container.addSubview(toView)
            }

            transitionContext.completeTransition(true)
    }
}

}

I assign my transitioning manager to the toViewController as it can be seen below:

var purchaseSpecialItemsViewController = self.storyboard?.instantiateViewControllerWithIdentifier("specialItemPurchaseVC") as! BRSpecialItemPurchaseViewController
    purchaseSpecialItemsViewController.transitioningDelegate = self.fadedTransitionManager

    self.presentViewController(purchaseSpecialItemsViewController, animated: true, completion: nil)

The View Controller I am about to display is in storyboard with a fixed size. It has a clear background and I added a tableview there that I want to be in the center of the screen.

The TableView is displayed without the problem, but I can't see the fromViewController at all. It is just black even though I set the alpha of the black background to 0 which is later animated to 0.5.

I am presenting the view controller modally, is that causing the problem? Should I use instead a push and pop operation?

Answer 1

As described here: http://mathewsanders.com/custom-menu-transitions-in-swift/

I needed to add the modal presentation style like this:

purchaseSpecialItemsViewController.modalPresentationStyle = UIModalPresentationStyle.OverFullScreen

and instead getting ViewControllersViews, use

let screens: (from: UIViewController, to: UIViewController) = (transitionContext.viewControllerForKey(UITransitionContextFromViewControllerKey)!, transitionContext.viewControllerForKey(UITransitionContextToViewControllerKey)!)

to access the ViewControllers.