UIViewに角丸枠線のUIBizierPath作る

この一年間やたらとUIBezierPathを使ったけど、稀によくあるUIViewいっぱいいっぱいに角丸枠線つけたい時に使うExtension

UIBezierPath+roundedCorner

extension UIBezierPath {

    static func roundedCorners(rect: CGRect, topLeft: CGFloat, topRight: CGFloat, bottomRight: CGFloat, bottomLeft: CGFloat, lineWidth: CGFloat) -> UIBezierPath {

        func radian(_ angle: CGFloat) -> CGFloat {
            return angle * CGFloat(Double.pi) / 180
        }

        let path = UIBezierPath()

        path.lineWidth = lineWidth

        let halfWidth = lineWidth/2

        path.move(to: CGPoint(x: topLeft + halfWidth, y: halfWidth))

        path.addLine(to: CGPoint(x: rect.maxX - halfWidth - topRight, y: halfWidth))
        path.addArc(withCenter: CGPoint(x: rect.maxX - halfWidth - topRight, y: topRight + halfWidth),
                    radius: topRight,
                    startAngle: radian(-90),
                    endAngle: radian(0),
                    clockwise: true)

        path.addLine(to: CGPoint(x: rect.maxX - halfWidth, y: rect.maxY - halfWidth - bottomRight))
        path.addArc(withCenter: CGPoint(x: rect.maxX - halfWidth - bottomRight, y: rect.maxY - halfWidth - bottomRight),
                    radius: bottomRight,
                    startAngle: radian(0),
                    endAngle: radian(90),
                    clockwise: true)

        path.addLine(to: CGPoint(x: bottomLeft + halfWidth, y: rect.maxY - halfWidth))
        path.addArc(withCenter: CGPoint(x: bottomLeft + halfWidth, y: rect.maxY - halfWidth - bottomLeft),
                    radius: bottomLeft,
                    startAngle: radian(90),
                    endAngle: radian(180),
                    clockwise: true)

        path.addLine(to: CGPoint(x: halfWidth, y: topLeft + halfWidth))
        path.addArc(withCenter: CGPoint(x: topLeft + halfWidth, y: topLeft + halfWidth),
                    radius: topLeft,
                    startAngle: radian(180),
                    endAngle: radian(270),
                    clockwise: true)

        return path
    }
}