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

Update: See this answer below for Swift 4 / iOS 11 which is much, much easier

---

Here's a quick Swift 3 extension you can use to do rounding and optional borders.

Note: if you're using autolayout, you may need to call this in one of the view lifecycle callbacks like viewDidLayoutSubviews or layoutSubviews after the view has been constrained.

import UIKit

extension UIView {
    
    /**
     Rounds the given set of corners to the specified radius
     
     - parameter corners: Corners to round
     - parameter radius:  Radius to round to
     */
    func round(corners: UIRectCorner, radius: CGFloat) {
        _ = _round(corners: corners, radius: radius)
    }
    
    /**
     Rounds the given set of corners to the specified radius with a border
     
     - parameter corners:     Corners to round
     - parameter radius:      Radius to round to
     - parameter borderColor: The border color
     - parameter borderWidth: The border width
     */
    func round(corners: UIRectCorner, radius: CGFloat, borderColor: UIColor, borderWidth: CGFloat) {
        let mask = _round(corners: corners, radius: radius)
        addBorder(mask: mask, borderColor: borderColor, borderWidth: borderWidth)
    }
    
    /**
     Fully rounds an autolayout view (e.g. one with no known frame) with the given diameter and border
     
     - parameter diameter:    The view's diameter
     - parameter borderColor: The border color
     - parameter borderWidth: The border width
     */
    func fullyRound(diameter: CGFloat, borderColor: UIColor, borderWidth: CGFloat) {
        layer.masksToBounds = true
        layer.cornerRadius = diameter / 2
        layer.borderWidth = borderWidth
        layer.borderColor = borderColor.cgColor;
    }
    
}

private extension UIView {
    
    @discardableResult func _round(corners: UIRectCorner, radius: CGFloat) -> CAShapeLayer {
        let path = UIBezierPath(roundedRect: bounds, byRoundingCorners: corners, cornerRadii: CGSize(width: radius, height: radius))
        let mask = CAShapeLayer()
        mask.path = path.cgPath
        self.layer.mask = mask
        return mask
    }
    
    func addBorder(mask: CAShapeLayer, borderColor: UIColor, borderWidth: CGFloat) {
        let borderLayer = CAShapeLayer()
        borderLayer.path = mask.path
        borderLayer.fillColor = UIColor.clear.cgColor
        borderLayer.strokeColor = borderColor.cgColor
        borderLayer.lineWidth = borderWidth
        borderLayer.frame = bounds
        layer.addSublayer(borderLayer)
    }
    
}