代码实现如下：
/// 风车视图的旋转
fileprivate func transformAnimation(view:UIView) {
let animation = CABasicAnimation(keyPath: "transform.rotation.z")
// 默认是顺时针效果，若将formValue和toValue的值互换，则为逆时针效果
animation.fromValue = 0
animation.toValue = Double.pi*2
animation.duration = 2
animation.autoreverses = false
// 解决动画结束后回到原始状态的问题
animation.isRemovedOnCompletion = false
animation.fillMode = kCAFillModeForwards
animation.repeatCount = MAXFLOAT // 一直旋转的话，就设置为MAXFLOAT
// 定义动画的节奏
// animation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseIn)
view.layer.add(animation, forKey: nil)
}
