Swift (2.3) CALayer extension to only round _some_ corners

CALayerExtension.swift

extension CALayer {
  func roundCorners(corners: UIRectCorner, radius: CGFloat) {
    let maskPath = UIBezierPath(roundedRect: bounds,
                                byRoundingCorners: corners,
                                cornerRadii: CGSize(width: radius, height: radius))

    let shape = CAShapeLayer()
    shape.path = maskPath.CGPath
    mask = shape
  }
}

// Usage:

myView.layer.roundCorners([.TopLeft, .TopRight], radius: myCornerRadius)