问如何在swift中为UIVIew制作曲线顶部？

EN

//TopRoundedCornerToView and BottomRoundedCornerToView

extension UIView {

func addTopRoundedCornerToView(targetView:UIView?, desiredCurve:CGFloat?)
{
    let offset:CGFloat =  targetView!.frame.width/desiredCurve!
    let bounds: CGRect = targetView!.bounds

    //Top side curve
    let rectBounds: CGRect = CGRect(x: bounds.origin.x, y: bounds.origin.y+bounds.size.height / 2, width: bounds.size.width, height: bounds.size.height / 2)

    let rectPath: UIBezierPath = UIBezierPath(rect: rectBounds)

    //Top side curve
    let ovalBounds: CGRect = CGRect(x: bounds.origin.x - offset / 2, y: bounds.origin.y, width: bounds.size.width + offset, height: bounds.size.height)

    let ovalPath: UIBezierPath = UIBezierPath(ovalIn: ovalBounds)
    rectPath.append(ovalPath)

    // Create the shape layer and set its path
    let maskLayer: CAShapeLayer = CAShapeLayer()
    maskLayer.frame = bounds
    maskLayer.path = rectPath.cgPath

    // Set the newly created shape layer as the mask for the view's layer
    targetView!.layer.mask = maskLayer
}

    func setTopCurve(){
           let offset = CGFloat(self.frame.size.height/4)
           let bounds = self.bounds
           let rectBounds = CGRect(x: bounds.origin.x, y: bounds.origin.y + bounds.size.height/2  , width:  bounds.size.width, height: bounds.size.height / 2)

           let rectPath = UIBezierPath(rect: rectBounds)

         let ovalBounds = CGRect(x: bounds.origin.x , y: bounds.origin.y - offset / 2, width: bounds.size.width + offset, height: bounds.size.height)
           let ovalPath = UIBezierPath(ovalIn: ovalBounds)
       rectPath.append(ovalPath)

           let maskLayer = CAShapeLayer.init()
           maskLayer.frame = bounds
           maskLayer.path = rectPath.cgPath
           self.layer.mask = maskLayer
       }

    func addBottomRoundedCornerToView(targetView:UIView?, desiredCurve:CGFloat?)
    {
        let offset:CGFloat =  targetView!.frame.width/desiredCurve!
        let bounds: CGRect = targetView!.bounds

        //Bottom side curve
        let rectBounds: CGRect = CGRect(x: bounds.origin.x, y: bounds.origin.y, width: bounds.size.width, height: bounds.size.height / 2)

        let rectPath: UIBezierPath = UIBezierPath(rect: rectBounds)

        //Bottom side curve
        let ovalBounds: CGRect = CGRect(x: bounds.origin.x - offset / 2, y: bounds.origin.y, width: bounds.size.width + offset, height: bounds.size.height)

        let ovalPath: UIBezierPath = UIBezierPath(ovalIn: ovalBounds)
        rectPath.append(ovalPath)

        // Create the shape layer and set its path
        let maskLayer: CAShapeLayer = CAShapeLayer()
        maskLayer.frame = bounds
        maskLayer.path = rectPath.cgPath

        // Set the newly created shape layer as the mask for the view's layer
        targetView!.layer.mask = maskLayer
    }

        func setBottomCurve(){
               let offset = CGFloat(self.frame.size.height/4)
               let bounds = self.bounds

            let rectBounds = CGRect(x: bounds.origin.x, y: bounds.origin.y  , width:  bounds.size.width, height: bounds.size.height / 2)
               let rectPath = UIBezierPath(rect: rectBounds)
               let ovalBounds = CGRect(x: bounds.origin.x - offset / 2, y: bounds.origin.y, width: bounds.size.width + offset, height: bounds.size.height)

               let ovalPath = UIBezierPath(ovalIn: ovalBounds)
           rectPath.append(ovalPath)

               let maskLayer = CAShapeLayer.init()
               maskLayer.frame = bounds
               maskLayer.path = rectPath.cgPath
               self.layer.mask = maskLayer
           }
}