Adding a visual effect to a SKSpriteNode when pressed

Question

I am working on my first SpriteKit app in Xcode 6, coding in Swift. Now I have made some nice buttons from transparent png files. But I am trying to show a visual effect when the button is pushed.

Example how I now show a static button:

let playButton = Button(imageNamed:"playButton")
playButton.position = CGPointMake(self.size.width/2, self.size.height/2 - playButton.size.height * 2.5 - displacement)
self.sharedInstance.addChildFadeIn(playButton, target: self)

Any effect would be enough, maybe a pulse effect, or glow on press. I've searched, but I can't really find anything in Swift.

edit: more info

    class Button: SKSpriteNode {  
        init(imageNamed: String) {
            let texture = SKTexture(imageNamed: imageNamed)
            // have to call the designated initializer for SKSpriteNode
            super.init(texture: texture, color: nil, size: texture.size())
        }
        override func touchesBegan(touches: NSSet, withEvent event: UIEvent) {
            self.runAction(SKAction.scaleTo(1.3, duration: kButtonFadingSpeed))
        }    
        override func touchesMoved(touches: NSSet, withEvent event: UIEvent) {
            self.runAction(SKAction.scaleTo(1.3, duration: kButtonFadingSpeed))
        }
         override func touchesEnded(touches: NSSet, withEvent event: UIEvent) {
            self.runAction(SKAction.scaleTo(1.0, duration: kButtonFadingSpeed))
        }

        required init(coder aDecoder: NSCoder) {
            fatalError("init(coder:) has not been implemented")
        }
}

    func addChildFadeIn(node: SKNode, target: SKNode) {
        node.alpha = 0
        target.addChild(node)
        node.runAction(SKAction.fadeAlphaTo(1.0, duration: NSTimeInterval(kAddChildSpeed)))
    }

The function AddChildFadeIn is defined in class: singleton

Any help is much appreciated!

Answer 1

I found a nice solution to this problem is to copy the original node, set the copy's alpha to 0.5 place it directly over top of the original node, and set its blendMode to add. here is a sample.

// this is our original node that we want to make glow
playButton.anchorPoint = CGPointMake(0.5, 0.5)

// create a copy of our original node create the glow effect
let glowNode : SKSpriteNode = playButton.copy() as! SKSpriteNode
glowNode.size = playButton.size
glowNode.anchorPoint = playButton.anchorPoint
glowNode.position = CGPoint(x: 0, y: 0)
glowNode.alpha = 0.5
glowNode.blendMode = SKBlendMode.Add

// add the new node to the original node
playButton.addChild(glowNode)

// add the original node to the scene
self.addChild(playButton)