Spawning an Enemy - swift

Question

In my game I want an enemy to spawn every 10 seconds. I attempt to accomplish this by, in the GameViewController, writing
var secondEnemyTimer = NSTimer.scheduledTimerWithTimeInterval(10.0, target: self, selector: "secondEnemyFunction", userInfo: nil, repeats: false)
in the viewWillLayoutSubviews method. Then in the secondEnemyFunction I write:
let skView = self.view as! SKView
let gameScene = GameScene(size: skView.bounds.size)
gameScene.enemy2Function()
Then in the enemy2Function in the GameScene class I write:
println("Called!")
enemy2.name = enemyCategoryName
enemy2.size.width = 57
enemy2.size.height = 57
let randomX = randomInRange(Int(CGRectGetMinX(self.frame)), hi: Int(CGRectGetMaxX(self.frame)))
let randomY = randomInRange(Int(CGRectGetMinY(self.frame)), hi: Int(CGRectGetMaxY(self.frame)))
let randomPoint = CGPoint(x: randomX, y: randomY)
enemy2.position = randomPoint
self.addChild(enemy2)
enemy2.physicsBody = SKPhysicsBody(circleOfRadius: enemy1.size.width / 2)
enemy2.physicsBody?.friction = 0
enemy2.physicsBody?.restitution = 1
enemy2.physicsBody?.linearDamping = 0
enemy2.physicsBody?.allowsRotation = false
enemy2.physicsBody?.applyImpulse(CGVectorMake(50, -50))
enemy2.physicsBody?.categoryBitMask = enemyCategory
In the log "Called!" appear yet the enemy is not spawned. Just so you know I did create the enemy at the top of the class by doing:
let enemy2 = SKSpriteNode(imageNamed: "enemy")
Does anyone know how I can spawn my second enemy? Thank you in advance!
-Vinny

Answer 1

You should keep things simple and just do everything inside GameScene. Another thing is to drop NSTimer and use SKAction to spawn enemies. NSTimer don't respect scene's paused state, so you can get into some trouble eventually. This is how you can spawn enemies using SKAction:
GameScene.swift:
import SpriteKit
class GameScene: SKScene {
override func didMoveToView(view: SKView) {
generateEnemies()
}
func stopGeneratingCoins(){
if(self.actionForKey("spawning") != nil){removeActionForKey("spawning")}
}
func generateEnemies(){
if(self.actionForKey("spawning") != nil){return}
let timer = SKAction.waitForDuration(10)
//let timer = SKAction.waitForDuration(10, withRange: 3)//you can use withRange to randomize duration
let spawnNode = SKAction.runBlock {
var enemy = SKSpriteNode(color: SKColor.greenColor(), size:CGSize(width: 40, height:40))
enemy.name = "enemy" // name it, so you can access all enemies at once.
//spawn enemies inside view's bounds
let spawnLocation = CGPoint(x:Int(arc4random() % UInt32(self.frame.size.width - enemy.size.width/2) ),
y:Int(arc4random() % UInt32(self.frame.size.height - enemy.size.width/2)))
enemy.position = spawnLocation
self.addChild(enemy)
println(spawnLocation)
}
let sequence = SKAction.sequence([timer, spawnNode])
self.runAction(SKAction.repeatActionForever(sequence) , withKey: "spawning") // run action with key so you can remove it later
}
}
When it comes to positioning, I assumed that your scene already has the correct size. If scene is not correctly initialized and has different size (or more precisely, different aspect ratio) than a view, it could happen that enemy get off-screen position when spawned. Read more here on how to initialize the scene size properly.