Create a rectangle with just two rounded corners in swift?

Question

I need to create a rectangle that have just two rounded corners in swift (Objective C code also ok).

At the moment my code is creating two rectangles with

Answer 1

iOS 11+ Only | You can check iOS usage stats here

Explanation

Since the CACornerMask rawValue is an UInt you know that a CACornerMask rawValue is the sum of each CACornerMask.Element rawValue

More specifically:

• TopLeft (layerMinXMinYCorner) = 1
• TopRight (layerMaxXMinYCorner) = 2
• BottomLeft (layerMinXMaxYCorner) = 4
• BottomRight (layerMaxXMaxYCorner) = 8

So for example if you want top left and top right corners you can just type CACornerMask(rawValue: 3).

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 Example

Below a simple extension of an UIView

extension UIView {
    enum Corner:Int {
        case bottomRight = 0,
        topRight,
        bottomLeft,
        topLeft
    }
    
    private func parseCorner(corner: Corner) -> CACornerMask.Element {
        let corners: [CACornerMask.Element] = [.layerMaxXMaxYCorner, .layerMaxXMinYCorner, .layerMinXMaxYCorner, .layerMinXMinYCorner]
        return corners[corner.rawValue]
    }
    
    private func createMask(corners: [Corner]) -> UInt {
        return corners.reduce(0, { (a, b) -> UInt in
            return a + parseCorner(corner: b).rawValue
        })
    }
    
    func roundCorners(corners: [Corner], amount: CGFloat = 5) {
        layer.cornerRadius = amount
        let maskedCorners: CACornerMask = CACornerMask(rawValue: createMask(corners: corners))
        layer.maskedCorners = maskedCorners
    }
}

You can use this like:

let myRect = UIView(frame: CGRect(x: 0, y: 0, width: 200, height: 50))
myRect.roundCorners(corners: [.topRight, .topLeft])