UIView圆角+阴影

backView是要添加阴影的视图，思路是backView设置corner圆角，再添加一个带阴影的父视图，代码如下：

                self.backView.layer.cornerRadius = 30;
                self.backView.layer.masksToBounds = true;
                
                let shadowView = UIView.init(frame: self.backView.frame)
                self.addSubview(shadowView)
                shadowView.layer.shadowColor = color;
                shadowView.layer.shadowOffset = CGSize(width:0, height:2);
                shadowView.layer.shadowOpacity = 1;
                shadowView.layer.shadowRadius = 4;
                shadowView.layer.cornerRadius = 30;
                shadowView.clipsToBounds = false;
                shadowView.addSubview(self.backView)

clipsToBounds这个属性的意思是子视图超出边界的区域是否裁剪