SpriteKit : Finding unexpectedly nil while unwrapping, can't implement multiple menu scenes - ios

Question

I am trying to present a menu with 2 buttons as initial scene: play, credits. When play is clicked, I want to present another menu scene with 4 buttons: tutorial, easy, hard, back.
The strategy is simply to create the buttons as SKSpriteNode objects and handle clicks in touchesBegan function.
In my menuScene.sks file I properly placed and named my nodes. Here, you can check the menuScene.swift file linked to this scene:
import SpriteKit
class menuScene: SKScene {
var playButton:SKSpriteNode!
var creditsButton:SKSpriteNode!
override func didMove(to view: SKView) {
playButton = self.childNode(withName: "playButton") as! SKSpriteNode
creditsButton = self.childNode(withName: "creditsButton") as! SKSpriteNode
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
// transition is defined in Helper.swift
let touch = touches.first
if let location = touch?.location(in: self){
let nodesArray = self.nodes(at: location)
if nodesArray.first?.name == "playButton" {
let nextScene = difScene(size: self.size)
self.view?.presentScene(nextScene, transition: transition)
} else if nodesArray.first?.name == "creditsButton" {
let nextScene = creditsScene(size: self.size)
self.view?.presentScene(nextScene, transition: transition)
}
}
}
}
When I run, menuScene is presented without a problem. However when I touch the play button I get an error and it is from next scene: difScene.
Here you can find difScene.swift:
import SpriteKit
class difScene: SKScene {
var tutButton:SKSpriteNode!
var easyButton:SKSpriteNode!
var hardButton:SKSpriteNode!
var backButton:SKSpriteNode!
override func didMove(to view: SKView) {
tutButton = self.childNode(withName: "tutButton") as! SKSpriteNode // error
easyButton = self.childNode(withName: "easyButton") as! SKSpriteNode
hardButton = self.childNode(withName: "hardButton") as! SKSpriteNode
backButton = self.childNode(withName: "backButton") as! SKSpriteNode
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
let transition = SKTransition.push(with: .down, duration: 0.2)
let touch = touches.first
if let location = touch?.location(in: self){
let nodesArray = self.nodes(at: location)
if nodesArray.first?.name == "tutButton" {
let nextScene = GameScene(size: self.size)
self.view?.presentScene(nextScene, transition: transition)
}
if nodesArray.first?.name == "easyButton" {
let nextScene = difScene(size: self.size)
self.view?.presentScene(nextScene, transition: transition)
}
if nodesArray.first?.name == "hardButton" {
let nextScene = difScene(size: self.size)
self.view?.presentScene(nextScene, transition: transition)
}
if nodesArray.first?.name == "backButton" {
let nextScene = menuScene(size: self.size)
self.view?.presentScene(nextScene, transition: transition)
}
}
}
}
In case it may be useful, here is my GameViewController.swift:
import UIKit
import SpriteKit
import GameplayKit
class GameViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
if let scene = GKScene(fileNamed: "menuScene") {
// Get the SKScene from the loaded GKScene
if let sceneNode = scene.rootNode as! menuScene? {
// Set the scale mode to scale to fit the window
sceneNode.scaleMode = .aspectFill
// Present the scene
if let view = self.view as! SKView? {
view.presentScene(sceneNode)
view.ignoresSiblingOrder = true
view.showsFPS = false
view.showsNodeCount = false
}
}
}
}
override var shouldAutorotate: Bool {
return true
}
override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
if UIDevice.current.userInterfaceIdiom == .phone {
return .allButUpsideDown
} else {
return .all
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Release any cached data, images, etc that aren't in use.
}
override var prefersStatusBarHidden: Bool {
return true
}
}
The error I get is:
Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value
I know this is not a unique error. I have Google'd, watched tutorials and tried to derive a solution from other StackOverflow threads but failed to overcome this.

Answer 1

The error is on this line
tutButton = self.childNode(withName: "tutButton") as! SKSpriteNode // error
because there is no child node with the name "tutButton", so force casting it to an SKSpriteNode causes the error.
When the play button is pressed, you call this code:
let nextScene = difScene(size: self.size)
self.view?.presentScene(nextScene, transition: transition)
This initializes a new difScene and presents it, which in turn calls the line of code above which is crashing.
Do you have a corresponding sks file for the difScene where you add the four buttons you reference in didMove?
If so, you'll need to initialize the difScene with the sks file like you did for your menu scene:
let scene = GKScene(fileNamed: "difScene")
If not, you'll need to create those four button nodes and add them as children to your scene programatically.
Side note: In Swift, the convention is to name types starting with capital letters. Your menuScene should be MenuScene, and your difScene should be DifScene. This will make it much easier for others to read and understand your code.