Passing data between SpriteKit scenes (Swift) - ios

Question

I have been following an old Ray Wenderlich tutorial: https://www.raywenderlich.com/1514-introduction-to-the-sprite-kit-scene-editor and have encountered a problem. I have run up against this problem numerous times and even found a "solution" on the stackoverflow site: Passing Data Between Scenes (SpriteKit)
This is the same code as the tutorial (with a few tweaks as it was written in Swift 2). I feel it a very simply elegant solution and not full of code using NSdefaults etc.
This is the call to the new scene, please note the soundToPlay object:
func gameOver(didWin: Bool) {
let menuScene = MenuScene(size: self.size)
menuScene.scaleMode = .aspectFill
menuScene.soundToPlay = didWin ? "fear_win.mp3" : "fear_lose.mp3"
let transition = SKTransition.flipVertical(withDuration: 1.0)
self.view?.presentScene(menuScene, transition: transition)
}
And this is the scene I am calling:
import SpriteKit
class MenuScene: SKScene {
var soundToPlay: String!
override func sceneDidLoad() {
self.backgroundColor = SKColor(red: 0, green:0, blue:0, alpha: 1)
// Setup label
let label = SKLabelNode(fontNamed: "AvenirNext-Bold")
label.text = "Press anywhere to play again!"
label.fontSize = 55
label.horizontalAlignmentMode = .center
label.position = CGPoint(x: self.frame.midX, y: self.frame.midY)
addChild(label)
// Play sound
if let soundToPlay = soundToPlay {
run(SKAction.playSoundFileNamed(soundToPlay, waitForCompletion: false))
}
}
The data is never passed and the object has a value of nil
I suspect it's something that has changed in Swift as the tutorial is very old as is the suggested "solution" on the previous stackoverflow question.
If that is the case, what is now the best way to achieve this?

Answer 1

The problem with your sound is that you are setting the variable after you call sceneDidLoad (this happens during init), so the sound will not play.
To fix this, do this code in your didMove method:
override func didMove(to view: SKView) {
guard let soundToPlay = soundToPlay else {fatalError("Unable to find soundToPlay")}
run(SKAction.playSoundFileNamed(soundToPlay, waitForCompletion: false))
}
The actual issue to your crashing is not visible here.
SKTransitions are bugged when you use SKLightNode, so by calling a scene with a transition, it is going to crash. SKTransitions have always been bugged with the introduction of Metal, so the only thing you can do is report it to apple and pray they do not tell you it is intentional.
As of now, keep track of all your light sources, and when you transition, set the isEnabled property to false.
You may need to create a screen shot of your scene prior to disabling the light source to not have it look silly.

Answer 2

What you are doing is, as you reload the scene (let menuScene = MenuScene(size: self.size)) you are resetting all the variables that were defined.
What you could do is use UserDefaults:
func gameOver(didWin: Bool) {
let menuScene = MenuScene(size: self.size)
menuScene.scaleMode = .aspectFill
let soundToPlay = didWin ? "fear_win.mp3" : "fear_lose.mp3"
UserDefaults.standard.set(soundToPlay, forKey: "soundToPlay")
let transition = SKTransition.flipVertical(withDuration: 1.0)
self.view?.presentScene(menuScene, transition: transition)
}
And:
import SpriteKit
class MenuScene: SKScene {
var soundToPlay: String!
override func sceneDidLoad() {
self.backgroundColor = SKColor(red: 0, green:0, blue:0, alpha: 1)
// Setup label
let label = SKLabelNode(fontNamed: "AvenirNext-Bold")
label.text = "Press anywhere to play again!"
label.fontSize = 55
label.horizontalAlignmentMode = .center
label.position = CGPoint(x: self.frame.midX, y: self.frame.midY)
addChild(label)
// Play sound
if let soundToPlay = UserDefaults.standard.string(forKey: "soundToPlay") {
run(SKAction.playSoundFileNamed(soundToPlay, waitForCompletion: false))
}
}
Then, put this in your AppDelegate's applicationWillTerminate function:
func applicationWillTerminate(_ application: UIApplication) {
// Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
UserDefaults.standard.removeObject(forKey: "soundToPlay")
}
If you do not put that in the AppDelegate then soundToPlay will remain after closing the app altogether.
I don't know if UserDefaults is the best way to do this, but I've struggled with this when I was making my iOS app and I just did this. So if anyone else has a better answer, please notify me as well!