Gameplaykit: Managing multiple objects using GKStatemachines - sprite-kit

Question

I'm writing a game that has a number of switch sprites that can be moved by the game player.I was intending to use a 'Game-play-kit' state machine to organize my code. I can't figure out how to manage multiple state machines - specifically I store my switches in an array, and each switch object includes a statemachine - how do I reference the 'parent' switch from within GKState classses in order to change it's properties(in this case running a new animation?)
This is my switch class:
class RailSwitch: SKSpriteNode {
var switchID: Int
var currentSwitchPosition: switchPosition
var initialSwitchPosition: switchPosition
var switchLocation: CGPoint
var isSwitchLocked: Bool
var isLeftMiddleSwitch: Bool
var currentAnimation: switchAnimation /* this is a dictionary of animation textures */
var stateMachine : GKStateMachine!
init(switchID: Int,
switchLocation: CGPoint,
initialSwitchPosition: switchPosition,
isSwitchLocked: Bool,
isLeftMiddleSwitch: Bool,
currentAnimation: switchAnimation,
texture:SKTexture!) {
self.switchID = switchID
self.switchLocation = switchLocation
self.initialSwitchPosition = initialSwitchPosition
self.currentSwitchPosition = initialSwitchPosition
self.isSwitchLocked = isSwitchLocked
self.isLeftMiddleSwitch = isLeftMiddleSwitch
self.currentAnimation = currentAnimation
super.init (texture: texture!, color: UIColor.clearColor(), size: texture!.size())
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
This is my switch Network class:
class SwitchNetwork {
var level : Int
var switchNetwork = [RailSwitch]()
var railSwitchAnimation : [switchAnimationState: switchAnimation]
init (level:Int) {
self.level = level
self.switchNetwork = []
self.railSwitchAnimation = [:]
}
func initialiseSwitches() {
/* one test example switch - in practice there will be many*/
railSwitchAnimation = loadSwitchAnimations()
switchNetwork.append(RailSwitch(switchID: 1,
switchLocation: CGPointMake(400,300),
initialSwitchPosition: (.left) ,
isSwitchLocked: false,
isLeftMiddleSwitch: true,
currentAnimation: railSwitchAnimation[.left]!,
texture: railSwitchAnimation[.left]!.textures[0]
))
}
I initiate the switches from within GameScene:
func initiateSwitchNetwork() {
for thisSwitch in 0 ... switches.switchNetwork.count - 1 {
switches.switchNetwork[thisSwitch].stateMachine = GKStateMachine(states: [
GameStart(scene: self),
SwitchLeft(scene: self),
SwitchRight(scene: self),
SwitchMiddle(scene: self),
SwitchLeftLocked(scene: self),
SwitchRightLocked(scene: self),
SwitchMiddleLocked(scene: self)])
switches.switchNetwork[thisSwitch].stateMachine.enterState(GameStart)
}
Here's my question.From within the switch statemachine gkstate classes, who do I change the animation?I need to access the parent switch object that holds the statemachine somehow?
class GameStart: GKState {
unowned let scene: GameScene
init(scene: SKScene) {
self.scene = scene as! GameScene
super.init()
}
override func didEnterWithPreviousState(previousState: GKState?) {
// scene.addChild(scene.switches.switchNetwork[0].currentAnimation.textures[0])
}
}

Answer 1

One approach to consider is instead of passing the scene into each state's init function, you could pass a reference to the parent switch instead? So your state's init function looks like this;
init(switch: RailSwitch) {
self.railSwitch = switch
super.init()
}
Then your RailSwitch might have a function to change the animation which you would call in the state's updateWithDeltaTime function.
override func updateWithDeltaTime(seconds: NSTimeInterval) {
self.railSwitch.changeAnimation(to switchTexture: .left)
}
Note that you have access to the stateMachine in each state;
override func updateWithDeltaTime(seconds: NSTimeInterval) {
self.stateMachine?.enterState(SwitchRight.self)
}
As an aside, I would prefer to use Strategy Pattern to implement this kind of functionality, unless a switches next state is strongly determined by current state. Strategy is better suited where an external factor will determine the next change.