How Can I increase radius of SKShapeNode by 1 pixel every second? - swift

Question

I am trying to write a function where I can increase SKShapeNode radius every second, but don't know how:(
var eRadius: CGFloat = 20
var eCircle = SKShapeNode()
override func didMove(to view: SKView) {
super.didMove(to: view)
eCircle = SKShapeNode(circleOfRadius: eRadius)
eCircle.strokeColor = .black
eCircle.glowWidth = 1.0
eCircle.fillColor = .white
eCircle.fillTexture = SKTexture(imageNamed: "e")
addChild(eCircle)
gameTimer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(addRadius), userInfo: nil, repeats: true)
}
#objc func addRadius(){
eRadius += 1
???? :(
}
Thank you!

Answer 1

Here's a working solution:
import SpriteKit
class GameScene: SKScene {
private var eRadius: CGFloat = 20
private var eCircle = SKShapeNode()
override func didMove(to view: SKView) {
eCircle.strokeColor = .black
eCircle.glowWidth = 1.0
eCircle.fillColor = .white
eCircle.fillTexture = SKTexture(imageNamed: "e")
addChild(eCircle)
run(SKAction.repeatForever(SKAction.sequence([SKAction.run {
self.updateCirclePath()
self.eRadius += 1
}, SKAction.wait(forDuration: 1.0)])))
}
private func updateCirclePath() {
eCircle.path = UIBezierPath(ovalIn: CGRect(x: -eRadius * 0.5, y: -eRadius * 0.5, width: eRadius, height: eRadius)).cgPath
}
}
Basically, you create the circle using a UIBezierPath and then update it as your radius changes. For the updating you should use a forever-repeating SKAction sequence that both sets the path, then changes the radius. I chose to do the path first, then update the radius for the next upcoming turn, for clarity.
You can also do it the opposite way, so run the update function first to set the initial path, then wait one second, after which you change the radius, then update the path based on that radius.
In SpriteKit, you should use SKActions for timers instead of scheduling or dispatch queues. With SKActions, everything conforms to the same game time, which you can then control by pausing and whatever.
Also, there are multiple ways to make a circle using UIBezierPath, including ovals, rounded rectangles and arcs: https://developer.apple.com/documentation/uikit/uibezierpath.