如何在CABasicAnimation旋转中添加减速度影响

Question

我正在堆栈溢出后This Answer之后使用CABasicAnimation使用Pan手势旋转视图。 我已经尝试过，但是没有找到减速旋转的确切方法。 fileprivate let rotationAnimation = CABasicAnimation（）

func rotate(to: CGFloat, duration: Double = 0) {
    rotateAnimation.fromValue = to
    rotateAnimation.toValue = to
    rotateAnimation.duration = duration
    rotateAnimation.repeatCount = 0
    rotateAnimation.isRemovedOnCompletion = false
    rotateAnimation.fillMode = kCAFillModeForwards
    rotateAnimation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionLinear)
    imageView.layer.add(rotateAnimation, forKey: "transform.rotation.z")
}



func angle(from location: CGPoint) -> CGFloat {
    let deltaY = location.y - view.center.y
    let deltaX = location.x - view.center.x
    let angle = atan2(deltaY, deltaX) * 180 / .pi
    return angle < 0 ? abs(angle) : 360 - angle
}


extension FloatingPoint {
    var degreesToRadians: Self { return self * .pi / 180 }
    var radiansToDegrees: Self { return self * 180 / .pi }
}

extension UserDefaults {
    /// rotation persistant computed property
    var rotation: CGFloat {
        get {
            return CGFloat(double(forKey: "rotation"))
        }
        set {
            set(Double(newValue), forKey: "rotation")
        }
    }
}

@objc func pan(_ gesture: UIPanGestureRecognizer) {
    let location = gesture.location(in: view)
    let gestureRotation = CGFloat(angle(from: location)) - startRotationAngle
    switch gesture.state {
    case .began:
        // set the start angle of rotation 
        startRotationAngle = angle(from: location)
    case .changed:
        rotate(to: rotation - gestureRotation.degreesToRadians)
    case .ended:
        // update the amount of rotation
        rotation -= gestureRotation.degreesToRadians
    default :
        break
    }
    // save the final position of the rotation to defaults
    UserDefaults.standard.rotation = rotation
}