Closure CallBack Only Retain Last Object Created in Swift - swift

Question

i'm not sure if the title fit my question but my question is as below.
First of all, i will talk how i encounter this problem. Basically, I'm creating a game(you can just imagine) which has A MainPlayer and Many Of Enemies(AI). So, the MainPlayer will move around and enemies will chase after him. As you can imagine, the MainPlayer's position will update in every frame(maybe) and i need also to update enemies' chasing position(which is main character's position). So i'm using Closure to do it. The reason why i'm not using array to store all the enemies and update it every frame is because the enemies can be killed and will random spawn new enemies in the amount of time i set. If i use array it is kind of tricky and unsafe.
So, back to my question, i created this beginning of GameScene class:
typealias CallBacks = () -> Void
var playerDidMoveCallBacks: CallBacks?
This is my create enemy class: (The callback is at most bottom)
// Create Enemies
func createEnemyAtPosition(position: CGPoint) {
let enemyNode = EnemyNode()
enemyNode.name = "ENEMY_NODE"
enemyNode.position = position
enemyNode.setScale(1.5)
addChild(enemyNode)
let sprite = SKSpriteNode(imageNamed: "enemyWisp")
enemyNode.addChild(sprite)
enemyNode.physicsBody = SKPhysicsBody(circleOfRadius: sprite.size.width / 2)
enemyNode.physicsBody?.dynamic = true
enemyNode.physicsBody?.categoryBitMask = CollisionCategoryBitMask.Enemy
enemyNode.physicsBody?.collisionBitMask = 0
enemyNode.physicsBody?.contactTestBitMask = CollisionCategoryBitMask.ThrowingKnife | CollisionCategoryBitMask.Player
enemyNode.physicsBody?.usesPreciseCollisionDetection = true
let distanceWillCollideWithPlayer = sqrt(pow(enemyNode.position.x - self.playerNode.position.x, 2) + pow(enemyNode.position.y - self.playerNode.position.y, 2))
let durationWillColldeWithPlayer = NSTimeInterval(distanceWillCollideWithPlayer / self.enemyMovingSpeed)
let enemyMoveAction = SKAction.moveTo(self.playerNode.position, duration: durationWillColldeWithPlayer)
enemyNode.runAction(enemyMoveAction)
println("\((unsafeAddressOf(enemyNode)))")
// Update Player Position
playerDidMoveCallBacks = {() -> Void in
let distanceWillCollideWithPlayer = sqrt(pow(enemyNode.position.x - self.playerNode.position.x, 2) + pow(enemyNode.position.y - self.playerNode.position.y, 2))
let durationWillColldeWithPlayer = NSTimeInterval(distanceWillCollideWithPlayer / self.enemyMovingSpeed)
println("\((unsafeAddressOf(enemyNode)))")
let enemyMoveAction = SKAction.moveTo(self.playerNode.position, duration: durationWillColldeWithPlayer)
enemyNode.runAction(enemyMoveAction)
}
}
When i know my hero changed position i call the callback like this:
if self.playerDidMoveCallBacks != nil {
self.playerDidMoveCallBacks!()
}
But this can only work for the last object created and i think this make sense. Anyone can give me a solution?

Answer 1

What you want is an array of callbacks.
var playerDidMoveCallBacks: [CallBack]?
As every enemy is captured in the closure you could just iterate the array and call each callback.
for callback in playerDidMoveCallBacks {
callback()
}
But the solution of 0x141E is better.
The problem is that the enemy could not exist anymore when you call the closure, but the closure captures the object which can lead to strange behaviour. (ghost enemies)

Answer 2

With help from 0x141E i create this line of code in func update and solve my problem
// Update Enemies Position
for childNode in children {
let childSprite = childNode as? SKNode
if (childSprite?.name == "ENEMY_NODE") {
let distanceWillCollideWithPlayer = sqrt(pow(CGFloat(childSprite!.position.x) - self.playerNode.position.x, 2) + pow(CGFloat(childSprite!.position.y) - self.playerNode.position.y, 2))
let durationWillColldeWithPlayer = NSTimeInterval(distanceWillCollideWithPlayer / self.enemyMovingSpeed)
let enemyMoveAction = SKAction.moveTo(self.playerNode.position, duration: durationWillColldeWithPlayer)
childSprite!.runAction(enemyMoveAction)
}
}