设置如图红色框里面的圆角样式，带边框：

extension UIView {

    //各圆角大小

    struct CornerRadii {

        vartopLeft:CGFloat=0

        vartopRight:CGFloat=0

        varbottomLeft:CGFloat=0

        varbottomRight:CGFloat=0

    }

    //切圆角函数绘制线条

    func createPathWithRoundedRect( bounds:CGRect,cornerRadii:CornerRadii) ->CGPath{

        let minX = bounds.minX

        let minY = bounds.minY

        let maxX = bounds.maxX

        let maxY = bounds.maxY

        //获取四个圆心

        let topLeftCenterX = minX+  cornerRadii.topLeft

        let topLeftCenterY = minY+cornerRadii.topLeft

        let topRightCenterX = maxX-cornerRadii.topRight

        let topRightCenterY = minY+cornerRadii.topRight

        let bottomLeftCenterX = minX +  cornerRadii.bottomLeft

        let bottomLeftCenterY = maxY - cornerRadii.bottomLeft

        let bottomRightCenterX = maxX-  cornerRadii.bottomRight

        let bottomRightCenterY = maxY-cornerRadii.bottomRight

        //虽然顺时针参数是YES，在iOS中的UIView中，这里实际是逆时针

        let path :CGMutablePath = CGMutablePath();

        //顶 左

        path.addArc(center:CGPoint(x: topLeftCenterX, y: topLeftCenterY), radius: cornerRadii.topLeft, startAngle:CGFloat.pi, endAngle:CGFloat.pi*3/2, clockwise:false)

        //顶右

        path.addArc(center:CGPoint(x: topRightCenterX, y: topRightCenterY), radius: cornerRadii.topRight, startAngle:CGFloat.pi*3/2, endAngle:0, clockwise:false)

        //底右

        path.addArc(center:CGPoint(x: bottomRightCenterX, y: bottomRightCenterY), radius: cornerRadii.bottomRight, startAngle:0, endAngle:CGFloat.pi/2, clockwise:false)

        //底左

        path.addArc(center:CGPoint(x: bottomLeftCenterX, y: bottomLeftCenterY), radius: cornerRadii.bottomLeft, startAngle:CGFloat.pi/2, endAngle:CGFloat.pi, clockwise:false)

        path.closeSubpath();

        returnpath;

    }

    //MARK:添加4个不同尺寸的圆角(可以设置边框)

    func addCorner(cornerRadii:CornerRadii, size:CGSize, borderColor:UIColor, borderWidth:CGFloat) {

        let rect =CGRect(origin:CGPoint(x:0, y:0), size: size)

        let path =createPathWithRoundedRect(bounds: rect, cornerRadii:cornerRadii)

        let shapLayer =CAShapeLayer()

        shapLayer.frame= rect

        shapLayer.path= path

        self.layer.mask= shapLayer

        //设置边框

        let borderLayer =CAShapeLayer()

        borderLayer.path= path

        borderLayer.fillColor=UIColor.clear.cgColor

        borderLayer.strokeColor= borderColor.cgColor

        borderLayer.lineWidth= borderWidth

        borderLayer.frame= rect

        self.layer.addSublayer(borderLayer)

    }

    //MARK:添加4个不同尺寸的圆角(不可以设置边框)

    func addCorner(cornerRadii:CornerRadii, size:CGSize) {

        let rect =CGRect(origin:CGPoint(x:0, y:0), size: size)

        let path =createPathWithRoundedRect(bounds: rect, cornerRadii:cornerRadii)

        let shapLayer =CAShapeLayer()

        shapLayer.frame= rect

        shapLayer.path= path

        self.layer.mask= shapLayer

    }

}