swift how make animation flip between two UIViews

I'm trying to create an IOS app and flip two views when pressing some buttons. I have found the flip animation but I want the flip to change the content to the new view when it is flipped 90° and not when the animation is completed. This is my function:

func animationFlip(fromView:UIView, toView:UIView, animationTime:Float)
{

    UIView.animateWithDuration(NSTimeInterval(animationTime), animations: {

        UIView.setAnimationTransition(UIViewAnimationTransition.FlipFromRight, forView: fromView, cache: true)

        },completion:{completion in
            UIView.animateWithDuration(NSTimeInterval(animationTime), animations: { () -> Void in

                fromView.hidden = true;
                toView.hidden = false;
                UIView.setAnimationTransition(UIViewAnimationTransition.FlipFromRight, forView: toView, cache: true)


            })
    })
}

I have found this code which seems to do the trick but it is written in obj-c. How can it be translated to swift?

[UIView transitionFromView:viewToReplace
        toView:replacementView
        duration:1
        options:UIViewAnimationOptionTransitionFlipFromBottom
        completion:nil];

Thanks in advance!