Swift Center on Camera not working when ApplyingImpulse in another class - swift

Question

I'm new to swift programming and have been stuck on this issue for the last week. I am trying to centre on a hero while applying impulse to him. My code works if I create a hero in the scene class and centre him but it doesn't work when I put a hero in another class and try to centre him from scene class. Now centre on works if I just move him by changing his x or y position but not if I apply impulse. It seems that when a hero is in a separate class, when impulse is applied x and y while he is in motion is showing up as a nil, however when he is in the same class than x and y while in the motion are showing up ok. Any help is much appreciated.
Code where Center ON works with ApplyImpulse when everything is in the same class*****
class GameScene: SKScene {
var hero:SKSpriteNode?
var mazeWorld:SKNode?
var player=Player()
var heroLocation:CGPoint = CGPointZero
override func didMoveToView(view: SKView) {
mazeWorld = childNodeWithName("mazeWorld")
heroLocation = mazeWorld!.childNodeWithName("sPoint")!.position
self.anchorPoint = CGPoint(x: 0.5,y: 0.3)
hero?.position = heroLocation
hero = SKSpriteNode(imageNamed:"hero_walk_down_0")
hero!.physicsBody?.dynamic = false
hero!.physicsBody?.affectedByGravity = true
hero!.physicsBody?.pinned = false
hero!.physicsBody = SKPhysicsBody(rectangleOfSize: hero!.size)
hero!.physicsBody?.mass = 1.0;
hero!.setScale(0.8)
mazeWorld!.addChild(hero!)
}
override func touchesBegan(touches: NSSet, withEvent event: UIEvent)
{
/* Called when a touch begins */
for touch: AnyObject in touches {
hero!.physicsBody?.applyImpulse(CGVector(dx: 240, dy: 550))
}
}
override func update(currentTime: CFTimeInterval) {
/* Called before each frame is rendered */
}
func centerOnNode(node:SKNode){
let cameraPositionInScene:CGPoint = self.convertPoint(node.position, fromNode: mazeWorld!)
mazeWorld!.position = CGPoint(x:mazeWorld!.position.x - cameraPositionInScene.x, y: mazeWorld!.position.y - cameraPositionInScene.y)
}
override func didSimulatePhysics() {
self.centerOnNode(hero!)
}
}
**** Here is the code with Center ON that doesn't work with apply impulse for some reason
import SpriteKit
class GameScene: SKScene {
var hero:SKSpriteNode?
var mazeWorld:SKNode?
var player=Player()
var heroLocation:CGPoint = CGPointZero
override func didMoveToView(view: SKView) {
mazeWorld = childNodeWithName("mazeWorld")
heroLocation = mazeWorld!.childNodeWithName("sPoint")!.position
self.anchorPoint = CGPoint(x: 0.5,y: 0.3)
player.position = heroLocation
mazeWorld!.addChild(player)
}
override func touchesBegan(touches: NSSet, withEvent event: UIEvent)
{
/* Called when a touch begins */
for touch: AnyObject in touches {
player.jumpRight()
}
}
override func update(currentTime: CFTimeInterval) {
/* Called before each frame is rendered */
}
func centerOnNode(node:SKNode){
let cameraPositionInScene:CGPoint = self.convertPoint(node.position, fromNode: mazeWorld!)
mazeWorld!.position = CGPoint(x:mazeWorld!.position.x - cameraPositionInScene.x, y: mazeWorld!.position.y - cameraPositionInScene.y)
}
override func didSimulatePhysics() {
self.centerOnNode(player)
}
}
import Foundation
import SpriteKit
class Player: SKNode{
var objectSprite:SKSpriteNode?
override init()
{
super.init()
objectSprite = SKSpriteNode(imageNamed:"hero_walk_down_0")
objectSprite!.physicsBody?.dynamic = false
objectSprite!.physicsBody?.affectedByGravity = true
objectSprite!.physicsBody?.pinned = false
objectSprite!.physicsBody = SKPhysicsBody(rectangleOfSize: objectSprite!.size)
objectSprite!.physicsBody?.mass = 1.0
objectSprite!.setScale(0.8)
addChild(objectSprite!)
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func jumpRight()
{
objectSprite!.physicsBody?.applyImpulse(CGVector(dx: 240, dy: 550))
}
}