SpriteKit: Updating several enemies position to follow the player - swift

Question

I found this answer on how to make the enemies move towards the player. If I have one enemy on the GameScene, it works perfect. However, if I add another enemy to the scene, only one of them moves while the other is stationary.
Here is the code on how I have everything set up so far.
var player: SKSpriteNode?
var spawnZombie = SKSpriteNode()
override func didMove(to view: SKView) {
playerTexture = SKTexture(imageNamed: "player_2")
player = SKSpriteNode(texture: playerTexture)
player?.name = "player"
player?.position = (pSpawnPoint?.position)!
player?.setScale(0.5)
self.addChild(player!)
randomEnemy()
randomEnemy()
}
This is how my enemies are set up
func randomEnemy(){
spawnPoint0 = childNode(withName: "spawnPoint_0") as? SKSpriteNode
spawnPoint1 = childNode(withName: "spawnPoint_1") as? SKSpriteNode
spawnPoint2 = childNode(withName: "spawnPoint_2") as? SKSpriteNode
// Set up enemies
enemy = SKSpriteNode(imageNamed: "enemy_2")
enemy.name = "enemy"
enemy.setScale(0.5)
enemy.zPosition = 10
enemy.physicsBody = SKPhysicsBody(rectangleOf: enemy.size)
enemy.physicsBody?.categoryBitMask = PhysicsCatagory.Enemy
enemy.physicsBody?.collisionBitMask = PhysicsCatagory.None
enemy.physicsBody?.contactTestBitMask = PhysicsCatagory.Player
enemy.physicsBody?.isDynamic = true
enemy.physicsBody?.affectedByGravity = false
let choice = Int(arc4random_uniform(3))
switch choice {
case 0:
enemy.position = (spawnPoint0?.position)!
self.addChild(enemy)
break
case 1:
enemy.position = (spawnPoint1?.position)!
self.addChild(enemy)
break
case 2:
enemy.position = (spawnPoint2?.position)!
self.addChild(enemy)
break
default:
print("something went wrong")
}
}
override func update(_ currentTime: TimeInterval) {
let location = player?.position
//Aim
let dx = (location?.x)! - enemy.position.x
let dy = (location?.y)! - enemy.position.y
let angle = atan2(dy, dx)
enemy.zRotation = angle - 3 * .pi/2
//Seek
let velocityX = cos(angle) * enemySpeed
let velocityY = sin(angle) * enemySpeed
enemy.position.x += velocityX
enemy.position.y += velocityY
}
Any ideas why only one of the enemies moves whenever I run the function twice? Thanks in advance.

Answer 1

you are putting both of your enemies in the same enemy variable. so when you try to move enemy you are basically moving the last one assigned to that variable.
what you need to do is put them in an array and then move all of the enemies from the array.
let enemies = [SKSpriteNode]()
func randomEnemy() {
//...other code blah blah blah
enemies.append(enemy)
}
and in the update func
override func update(_ currentTime: TimeInterval) {
let location = player?.position
for enemy in enemies {
//Aim
let dx = (location?.x)! - enemy.position.x
let dy = (location?.y)! - enemy.position.y
let angle = atan2(dy, dx)
enemy.zRotation = angle - 3 * .pi/2
//Seek
let velocityX = cos(angle) * enemySpeed
let velocityY = sin(angle) * enemySpeed
enemy.position.x += velocityX
enemy.position.y += velocity
}
}
now you probably want to look at sub classing enemy and having the move functionality in that class but that is outside the scope of your question. This should get you started.