vibrated.swift

// based on this article. http://qiita.com/magickworx/items/9a8e6108db8134a8363a#comment-f7c2edf79151a38f4d9d

extension Double {
    func toRadians() -> Double {
        return self * Double(M_PI) / 180
    }
}

extension UIView {
    private struct Const {
        static let VibrateAnimationKey = "VibrateAnimationKey"
        static let TransformRotationKeyPath = "transform.rotation"
    }
    func vibrated(vibrated: Bool) {
        guard vibrated else {
            layer.removeAnimationForKey(Const.VibrateAnimationKey)
            return
        }
        let animation = CABasicAnimation(keyPath: Const.TransformRotationKeyPath)
        animation.duration = 0.25
        animation.fromValue = 3.0.toRadians()
        animation.toValue = -3.0.toRadians()
        animation.repeatCount = .infinity
        animation.autoreverses = true
        layer.addAnimation(animation, forKey: Const.VibrateAnimationKey)
    }
}