UIButton Extension

SpringButton-Extension.swift

import UIKit
import Spring

var _scaleFactor: CGFloat = 1

public extension SpringButton {
    
    @nonobjc static let scaleTo = "_scaleTo"
    @nonobjc static let scaleBack = "_scaleBack"
    
    public func addTargetForAnimation(scaleFactor: CGFloat?) {
        _scaleFactor = scaleFactor!
        addTarget(self, action: Selector(SpringButton.scaleTo), forControlEvents: .TouchDown)
        addTarget(self, action: Selector(SpringButton.scaleBack), forControlEvents: .TouchUpInside)
        addTarget(self, action: Selector(SpringButton.scaleBack), forControlEvents: .TouchDragExit)
    }
    
    func _scaleTo() {
        self.scaleX = _scaleFactor
        self.scaleY = _scaleFactor
        self.animateTo()
    }
    
    func _scaleBack() {
        self.scaleX = 1
        self.scaleY = 1
        self.animateTo()
    }
    
}

UIButton-Extension.swift

import UIKit

var _scaleFactor: CGFloat = 1

public extension UIButton {
    
    @nonobjc static let scaleTo = "_scaleTo"
    @nonobjc static let scaleBack = "_scaleBack"
    
    public func addTargetForAnimation(scaleFactor: CGFloat?) {
        _scaleFactor = scaleFactor!
        addTarget(self, action: Selector(UIButton.scaleTo), forControlEvents: .TouchDown)
        addTarget(self, action: Selector(UIButton.scaleBack), forControlEvents: .TouchUpInside)
        addTarget(self, action: Selector(UIButton.scaleBack), forControlEvents: .TouchDragExit)
    }
    
    func _scaleTo() {
        UIView.animateWithDuration(0.1) {
            self.transform = CGAffineTransformMakeScale(_scaleFactor, _scaleFactor)
        }
    }
    
    func _scaleBack() {
        UIView.animateWithDuration(0.1) {
            self.transform = CGAffineTransformIdentity
        }
    }
    
}