扩展CA角掩码{

static let allCorners: CACornerMask = [.layerMinXMinYCorner, .layerMinXMaxYCorner, .layerMaxXMinYCorner, .layerMaxXMaxYCorner]

}
扩展CA角掩码{

init(_ rectCorner: UIRectCorner) {
    let corners = Self.from(rectCorner)
    self.init([corners])
}

func toUIRectCorner() -> UIRectCorner {
    UIRectCorner(self)
}

static func from(_ rectCorner: UIRectCorner) -> CACornerMask {
    var caCorners = CACornerMask()
    if rectCorner.contains(.allCorners) {
        caCorners = .allCorners
    } else {
        if rectCorner.contains(.topRight) {
            caCorners.insert(.layerMaxXMinYCorner)
        }
        
        if rectCorner.contains(.topLeft) {
            caCorners.insert(.layerMinXMinYCorner)
        }
        
        if rectCorner.contains(.bottomRight) {
            caCorners.insert(.layerMaxXMaxYCorner)
        }
        
        if rectCorner.contains(.bottomLeft) {
            caCorners.insert(.layerMinXMaxYCorner)
        }
    }
    return caCorners
}

}
扩展名UIRectCorner {

init(_ caCorners: CACornerMask) {
    let corners = Self.from(caCorners)
    self.init([corners])
}

func toCACornerMask() -> CACornerMask {
    CACornerMask(self)
}

static func from(_ corners: CACornerMask) -> UIRectCorner {
    var rectCorners = UIRectCorner()
    if corners.contains(.layerMinXMinYCorner) {
        rectCorners.insert(.topLeft)
    }
    
    if corners.contains(.layerMaxXMinYCorner) {
        rectCorners.insert(.topRight)
    }
    
    if corners.contains(.layerMinXMaxYCorner) {
        rectCorners.insert(.bottomLeft)
    }
    
    if corners.contains(.layerMaxXMaxYCorner) {
        rectCorners.insert(.bottomRight)
    }
    return rectCorners
}

}

将UIRectCorner转换为CACornerMask

extension UIRectCorner {
    
    /// convert UIRectCorner to CACornerMask
    var caCornerMask: CACornerMask {
        var cornersMask = CACornerMask()
        if self.contains(.topLeft) {
            cornersMask.insert(.layerMinXMinYCorner)
        }
        if self.contains(.topRight) {
            cornersMask.insert(.layerMaxXMinYCorner)
        }
        if self.contains(.bottomLeft) {
            cornersMask.insert(.layerMinXMaxYCorner)
        }
        if self.contains(.bottomRight) {
            cornersMask.insert(.layerMaxXMaxYCorner)
        }
        return cornersMask
    }
}

像这样使用

let rectCorner: UIRectCorner = [.topLeft, .bottomRight]
let cornerMask = rectCorner.caCornerMask
//result in cornerMask = [.layerMinXMinYCorner, .layerMaxXMaxYCorner]