Как получить атрибут с помощью парсера XMLPull

extension CALayer {

    func shake(duration: NSTimeInterval = NSTimeInterval(0.5)) {

        let animationKey = "shake"
        removeAnimationForKey(animationKey)

        let kAnimation = CAKeyframeAnimation(keyPath: "transform.translation.x")
        kAnimation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionLinear)
        kAnimation.duration = duration

        var needOffset = CGRectGetWidth(frame) * 0.15,
        values = [CGFloat]()

        let minOffset = needOffset * 0.1

        repeat {

            values.append(-needOffset)
            values.append(needOffset)
            needOffset *= 0.5
        } while needOffset > minOffset

        values.append(0)
        kAnimation.values = values
        addAnimation(kAnimation, forKey: animationKey)
    }
}

Как использовать:

[UIView, UILabel, UITextField, UIButton & etc].layer.shake(NSTimeInterval(0.7))