UIButton subclass where borderRadius can be set for each corner individually

BorderedButton.swift

//
//  BorderedButton.swift
//
//  A UIButton subclass where you can choose which corners (top left, top right,
//  bottom left, bottom right) of the button you want to have a borderRadius on.
//  Either set these in code or in Interface Builder.
//

import UIKit

@IBDesignable
class BorderedButton: UIButton {

    @IBInspectable var borderColor: UIColor = UIColor(red:0.020,  green:0.522,  blue:1, alpha:1)
    @IBInspectable var borderWidth: CGFloat = 1
    @IBInspectable var cornerRadius: CGFloat = 4
    
    @IBInspectable var roundCornerTopLeft: Bool = true
    @IBInspectable var roundCornerTopRight: Bool = true
    @IBInspectable var roundCornerBottomLeft: Bool = true
    @IBInspectable var roundCornerBottomRight: Bool = true
    
    private var borderLayer = CAShapeLayer()
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        setupView()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        setupView()
    }
    
    func setupView() {
        borderLayer.strokeColor = borderColor.CGColor
        borderLayer.borderWidth = borderWidth
        borderLayer.fillColor = UIColor.whiteColor().colorWithAlphaComponent(0).CGColor
        
        layer.insertSublayer(borderLayer, atIndex: 0)
    }
    
    override func layoutSubviews() {
        super.layoutSubviews()
        
        var rectCorners: UIRectCorner = []
        
        if roundCornerTopLeft { rectCorners.insert(.TopLeft) }
        if roundCornerTopRight { rectCorners.insert(.TopRight) }
        if roundCornerBottomLeft { rectCorners.insert(.BottomLeft) }
        if roundCornerBottomRight { rectCorners.insert(.BottomRight) }
        
        let borderPath = UIBezierPath(roundedRect: self.bounds, byRoundingCorners: rectCorners, cornerRadii: CGSize(width: cornerRadius, height: cornerRadius))
        borderLayer.path = borderPath.CGPath
    }

}