iOS / Swift - IBDesignable and IBInspectable working example for a UIButton subclass with a border

BorderButton.swift

import UIKit

@IBDesignable
class BorderButton: UIButton {

    @IBInspectable var cornerRadius: CGFloat = 0 {
        didSet {
            layer.cornerRadius = cornerRadius
            layer.masksToBounds = cornerRadius > 0
        }
    }
    @IBInspectable var borderWidth: CGFloat = 0 {
        didSet {
            layer.borderWidth = borderWidth
        }
    }
    @IBInspectable var borderColor: UIColor? = UIColor.clearColor() {
        didSet {
            layer.borderColor = borderColor?.CGColor
        }
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
    }

}