SpriteKit: Resizable circle with a ripple effect animation

RippleCircleNode.swift

//
//  RippleCircleNode.swift
//
//  Created by Rasmus Styrk on 14/09/2018.
//  Copyright © 2018 House of Code ApS. All rights reserved.
//
// Updated https://gist.github.com/gblancogarcia/4b8c22dd9f0272edde86
//  - Swift 4.2
//  - Made fade out a bit slower
//  - Changed scale paramater to newRadius instead
//  - Added completion to be called when animation finished so you can repeat the ripple

import SpriteKit

class RippleCircleNode: SKShapeNode {
    
    var radius: CGFloat {
        didSet {
            self.path = RippleCircleNode.path(radius: self.radius)
        }
    }
    
    init(radius: CGFloat, position: CGPoint) {
        self.radius = radius
        super.init()
        self.path = RippleCircleNode.path(radius: self.radius)
        self.position = position
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    class func path(radius: CGFloat) -> CGMutablePath {
        let path: CGMutablePath = CGMutablePath()
        
        path.addArc(center: CGPoint(x: 0, y: 0),
                    radius: radius,
                    startAngle: 0.0,
                    endAngle: CGFloat(2.0 * M_PI),
                    clockwise: true)
        
        return path
    }
    
    func ripple(to newRadius: CGFloat, duration: TimeInterval, completion: @escaping () -> ()) {
        if let parent = self.parent {
            let currentRadius = radius
            
            let circleNode = RippleCircleNode(radius: radius, position: position)
            circleNode.strokeColor = strokeColor
            circleNode.fillColor = fillColor
            circleNode.position = position
            circleNode.zRotation = zRotation
            circleNode.lineWidth = lineWidth
            circleNode.isUserInteractionEnabled = false
            
            if let index = parent.children.firstIndex(of: self) {
                parent.insertChild(circleNode, at: index)
                
                let scaleAction = SKAction.customAction(withDuration: duration,
                                                        actionBlock: { node, elapsedTime in
                                                            
                    let circleNode = node as! RippleCircleNode
                    let fraction = elapsedTime / CGFloat(duration)
                    circleNode.radius = currentRadius + (fraction * newRadius)
                })
                
                let fadeAction = SKAction.fadeAlpha(to: 0, duration: duration * 1.5)
                fadeAction.timingMode = SKActionTimingMode.easeOut
                
                let actionGroup = SKAction.group([scaleAction, fadeAction])
                
                circleNode.run(actionGroup, completion: {
                    circleNode.removeFromParent()
                    completion()
                })
            }
        }
    }
}