Swift: Button with closures as actions

FRButton Usage.md

let button = FRButton()

button.touchDownAction = {(button: FRButton) in
  print("button touchDownAction")
}

button.touchUpAction = {(button: FRButton) in
  print("button touchUpAction")
}


button.touchExitAction = {(button: FRButton) in
  print("button touchExitAction")
}

FRButton.swift

//
// Button with:
// - designable cornerRadius
// - designable borderWidth
// - designable borderColor
// - optional actions for touchDown, touchExit, touchUp
//

import UIKit

typealias FRButtonAction = (FRButton) -> Void

@IBDesignable

public class FRButton: UIButton {
    
    var touchDownAction: FRButtonAction?
    var touchUpAction: FRButtonAction?
    var touchExitAction: FRButtonAction?
    
    public required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        setupActions()
    }
    
    public override init(frame: CGRect) {
        super.init(frame: frame)
        setupActions()
    }
    
    @IBInspectable var borderWidth: CGFloat = 0.0 {
        didSet {
            layer.borderWidth = borderWidth
        }
    }

    @IBInspectable var borderColor: UIColor? {
        didSet {
            layer.borderColor = borderColor?.cgColor
        }
    }
    
    @IBInspectable override var cornerRadius: CGFloat {
        didSet {
            layer.cornerRadius = cornerRadius
            layer.masksToBounds = cornerRadius > 0
        }
    }
}

extension FRButton {
    
    func setupActions() {
        addTarget(self, action: #selector(touchDown(sender:)), for: [.touchDown, .touchDragEnter])
        addTarget(self, action: #selector(touchExit(sender:)), for: [.touchCancel, .touchDragExit])
        addTarget(self, action: #selector(touchUp(sender:)), for: [.touchUpInside])
    }
    
    //actions
    func touchDown(sender: FRButton) {
        touchDownAction?(sender)
    }
    
    func touchExit(sender: FRButton) {
        touchExitAction?(sender)
    }
    
    func touchUp(sender: FRButton) {
        touchUpAction?(sender)
    }
}