My SKSpriteNode speed values are not updating properly - swift

Question

What I'm trying to do is update my SKSpriteNodes so I can change their scrolling speeds dynamically, however they aren't really working consistently. I didn't include the code, but I have another method with a switch case that sets the value of platformSpeed whenever the state is changed (in this case, the switch case is changed with UIButtons). In my code I have an SKSpriteNode array and a platformSpeed property that includes didSet so my value is updated properly.
In my method to create the platforms, I grouped my SpriteNodes into platformGroup then looped through them with addChild(). Not sure why it's acting this way but here's a quick video of what it looks like in action:
demonstration clip
So with the buttons I'm changing the switch case, and as you can see, not all of the nodes speeds are updating properly and some get faster than others and eventually pass them. I need them to stay equal distance between each other.
Now here's my code:
class GameScene: SKScene, SKPhysicsContactDelegate {
var platformGroup = [SKSpriteNode]()
var platformSpeed: CGFloat = 1.0 {
didSet {
for platforms in platformGroup {
platforms.speed = platformSpeed
}
}
}
let platformTexture = SKTexture(imageNamed: "platform")
var platformPhysics: SKPhysicsBody!
func createPlatforms() {
let platformLeft = SKSpriteNode(texture: platformTexture)
platformLeft.physicsBody = platformPhysics.copy() as? SKPhysicsBody
platformLeft.physicsBody?.isDynamic = false
platformLeft.scale(to: CGSize(width: platformLeft.size.width * 4, height: platformLeft.size.height * 4))
platformLeft.zPosition = 20
let platformRight = SKSpriteNode(texture: platformTexture)
platformRight.physicsBody = platformPhysics.copy() as? SKPhysicsBody
platformRight.physicsBody?.isDynamic = false
platformRight.scale(to: CGSize(width: platformRight.size.width * 4, height: platformRight.size.height * 4))
platformRight.zPosition = 20
let scoreNode = SKSpriteNode(color: UIColor.clear, size: CGSize(width: frame.width, height: 32))
scoreNode.physicsBody = SKPhysicsBody(rectangleOf: scoreNode.size)
scoreNode.physicsBody?.isDynamic = false
scoreNode.name = "scoreDetect"
scoreNode.zPosition = 40
platformGroup = [platformLeft, platformRight, scoreNode]
let yPosition = frame.width - platformRight.frame.width
let max = CGFloat(frame.width / 4)
let xPosition = CGFloat.random(in: -80...max)
let gapSize: CGFloat = -50
platformLeft.position = CGPoint(x: xPosition + platformLeft.size.width - gapSize, y: -yPosition)
platformRight.position = CGPoint(x: xPosition + gapSize, y: -yPosition)
scoreNode.position = CGPoint(x: frame.midX, y: yPosition - (scoreNode.size.width / 1.5))
let endPosition = frame.maxY + (platformLeft.frame.height * 3)
let moveAction = SKAction.moveBy(x: 0, y: endPosition, duration: 7)
let moveSequence = SKAction.sequence([moveAction, SKAction.removeFromParent()])
for platforms in platformGroup {
addChild(platforms)
platforms.run(moveSequence)
}
platformCount += 1
}
func loopPlatforms() {
let create = SKAction.run { [unowned self] in
self.createPlatforms()
platformCount += 1
}
let wait = SKAction.wait(forDuration: 1.1)
let sequence = SKAction.sequence([create, wait])
let repeatForever = SKAction.repeatForever(sequence)
run(repeatForever)
}

Answer 1

I think I can see what's going wrong. When you change platformSpeed, it changes the speed of all the platforms in platformGroup. And createPlatforms() is being called multiple times. Now, each time it's called you create a pair of platforms and assign these to platformGroup. Since you call the function multiple times, it's overwriting any existing values in the array. That's why changing platformSpeed only updates the speed of the latest platforms you've created---the older platforms stay the same speed because they're not in platformGroup anymore.
To fix this, my advice would be to have platformGroup store all the platforms currently on the screen. You could do this by changing
platformGroup = [platformLeft, platformRight, scoreNode]
to something like
let newNodes = [platformLeft, platformRight, scoreNode]
platformGroup += newNodes
// Alternatively, platformGroup.append(contentsOf: newNodes)
Now you need to make sure you're 1) only adding the new nodes to the scene, and 2) removing the old nodes from platformGroup when they're removed from the parent. You could do this by changing
let moveAction = SKAction.moveBy(x: 0, y: endPosition, duration: 7)
let moveSequence = SKAction.sequence([moveAction, SKAction.removeFromParent()])
for platforms in platformGroup {
addChild(platforms)
platforms.run(moveSequence)
}
to something like
let moveAction = SKAction.moveBy(x: 0, y: endPosition, duration: 7)
for node in newNodes {
let moveSequence = SKAction.sequence([
moveAction,
SKAction.removeFromParent(),
SKAction.run {
self.platformGroup.remove(node)
}
])
addChild(node)
node.run(moveSequence)
}
Now that you're keeping a track of all platforms ever made, your speed changes should be applied consistently to every platform on the screen. Hope this works!