ios – 停止CALayer影子影响子视图？

@H_450_1@我有一个定制的UIControl,我希望它有一个阴影,所以我设置相关属性在它的图层.在视图周围出现阴影,但阴影也会出现在UILabel的文本下,该文本是子视图.你如何阻止这个？我只想要外部超级视野的影子.

...
init() {        
    label = UILabel()
    label.translatesAutoresizingMaskIntoConsTraints = false
    self.translatesAutoresizingMaskIntoConsTraints = false
    addSubview(label)

    self.layer.masksToBounds = false
    self.layer.shadowColor = UIColor.blackColor().CGColor
    self.layer.shadowOpacity = 1.0
    self.layer.shadowRadius = 2.0

    // Adding these lines trying to explicitly stop shadow on label...
    label.layer.shadowOpacity = 0
    label.layer.shadowColor = nil
    ...
}