ios swift custom transition to darken fromViewController - ios

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.