fade between two UIButton images

Question

i want to fade between two UIButton images for the purpose of setting favorites in a UITableView.

Currently the transition is done without effect - it just changes t

Answer 1

@SuperDuperTango's answer with tintColor added:

extension UIButton {
    func changeImageAnimated(image: UIImage?) {
        guard let imageView = self.imageView, currentImage = imageView.image, newImage = image else {
            return
        }
        CATransaction.begin()
        CATransaction.setCompletionBlock {
            self.setImage(newImage, forState: UIControlState.Normal)
        }
        let crossFade: CABasicAnimation = CABasicAnimation(keyPath: "contents")
        crossFade.duration = 0.3
        crossFade.fromValue = currentImage.CGImage
        crossFade.toValue = newImage.CGImage
        crossFade.removedOnCompletion = false
        crossFade.fillMode = kCAFillModeForwards
        imageView.layer.addAnimation(crossFade, forKey: "animateContents")
        CATransaction.commit()

        let crossFadeColor: CABasicAnimation = CABasicAnimation(keyPath: "contents")
        crossFadeColor.duration = 0.3
        crossFadeColor.fromValue = UIColor.blackColor()
        crossFadeColor.toValue = UIColor(red: 232.0/255.0, green: 85.0/255.0, blue: 71.0/255.0, alpha: 1.0)
        crossFadeColor.removedOnCompletion = false
        crossFadeColor.fillMode = kCAFillModeForwards
        imageView.layer.addAnimation(crossFadeColor, forKey: "animateContents")
        CATransaction.commit()
    }
}