Round only top or bottom corners of a UIView

gistfile1.txt

extension UIView {
    enum Corners {
        case Top
        case Bottom
    }
    
    func roundCorners(radius : CGFloat, corners : Corners) {
        let radius : CGFloat = radius
        var maskFrame = self.bounds
        maskFrame.size.height += radius
        if corners == .Bottom { maskFrame.origin.y -= radius }
        let maskLayer : CALayer = CALayer()
        maskLayer.backgroundColor = UIColor.whiteColor().CGColor
        maskLayer.cornerRadius = radius
        maskLayer.frame = maskFrame
        self.layer.mask = maskLayer
    }
}