Sam Sam - 1 year ago 242
Swift Question

Building a SpriteKit/GameKit leaderboard within a specific scene

I'm pretty new to Swift and I'm having some trouble implementing a leaderboard into my game. I just watched a tutorial: 'Game Center Leaderboards! (Swift 2 in Xcode)' in which the GameCenter information all went through the one view of the app. In my game, I want the user to be able to play the game and then only when they are on a specific

will they have access to GameCenter.

So for example, on the
will they be user authenticated and also will be able to upload their high score. I think I'm also missing some of the differences between the
(where all of the tutorials logic is located) and one of my many scenes that I've made.

Here is my code in which I attempt to use the
on the
and create the various functions to reach GameCenter. The call is made when the user taps a certain label in the view: (this clearly doesnt work as I'm trying to access a scene on lines like this:
self.presentViewController(view!, animated:true, completion: nil)

class GameOverScene: SKScene, GKGameCenterControllerDelegate {

init(size: CGSize, theScore:Int) {
score = theScore
super.init(size: size)

override func didMoveToView(view: SKView) {


leaderboardLabel.text = "Tap for Leaderboard"
leaderboardLabel.fontSize = 12
leaderboardLabel.fontColor = SKColor.redColor()
leaderboardLabel.position = CGPoint(x: size.width*0.85, y: size.height*0.1)


override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {

for touch : AnyObject in touches {
let location = touch.locationInNode(self)

if(CGRectContainsPoint(leaderBoardLabel.frame, location)){

func authPlayer(){

//Create a play
let localPlayer = GKLocalPlayer.localPlayer()

//See if signed in or not
localPlayer.authenticateHandler = {
//A view controller and an error handler
(view,error) in

//If there is a view to work with
if view != nil {
self.presentViewController(view!, animated:true, completion: nil) //we dont want a completion handler


//Call this when ur highscore should be saved
func saveHighScore(number:Int){


let scoreReporter = GKScore(leaderboardIdentifier: "scoreBoard")
scoreReporter.value = Int64(number)

let scoreArray: [GKScore] = [scoreReporter]

GKScore.reportScores(scoreArray, withCompletionHandler: nil)



func showLeaderBoard(){

let viewController = self.view.window?.rootViewController
let gcvc = GKGameCenterViewController()

gcvc.gameCenterDelegate = self

viewController?.presentViewController(gcvc, animated: true, completion: nil)


func gameCenterViewControllerDidFinish(gameCenterViewController: GKGameCenterViewController) {
gameCenterViewController.dismissViewControllerAnimated(true, completion: nil)

Any advice on how I could go about this would be great, I think that I may be getting the whole scene/view controller mixed up and its leading to problems. Thanks!

Answer Source

This answer partially carries off on where we left off in the comments, since you didn't post your entire code I can't tell exactly where your hangup was, but this is what I put together along with a separate guide (it's a slightly different version of the code you post):

Author of most of the code:


import UIKit
import SpriteKit
import GameKit

class GameViewController: UIViewController {

    func authenticateLocalPlayer() {
        let localPlayer = GKLocalPlayer.localPlayer()
        localPlayer.authenticateHandler = {(viewController, error) -> Void in

            if (viewController != nil) {
                self.presentViewController(viewController!, animated: true, completion: nil)
            else {

    override func viewDidLoad() {


        //... The rest of the default code

    //... The rest of the default code

GameScene.swift (or whichever scene you want to use GC):

import SpriteKit
import GameKit
import UIKit

// Global scope (I generally put these in a new file called Global.swift)
var score = 0

//sends the highest score to leaderboard
func saveHighscore(gameScore: Int) {
    print ("You have a high score!")
    print("\n Attempting to authenticating with GC...")

    if GKLocalPlayer.localPlayer().authenticated {
        print("\n Success! Sending highscore of \(score) to leaderboard")

        //---------PUT YOUR ID HERE:
        //                          |
        //                          |
        //                          V
        let my_leaderboard_id = "YOUR_LEADERBOARD_ID"
        let scoreReporter = GKScore(leaderboardIdentifier: my_leaderboard_id)

        scoreReporter.value = Int64(gameScore)
        let scoreArray: [GKScore] = [scoreReporter]

        GKScore.reportScores(scoreArray, withCompletionHandler: {error -> Void in
            if error != nil {
                print("An error has occured:")
                print("\n \(error) \n")

// Your scene:
class GameScene: SKScene, GKGameCenterControllerDelegate {

    // Local scope variables (for this scene):

    // Declare a new node, then initialize it
    let call_gc_node   = SKLabelNode(fontNamed:"Chalkduster")
    let add_score_node = SKLabelNode(fontNamed: "Helvetica")

    override func didMoveToView(view: SKView) {

        // Give our GameCenter node some stuff
        initGCNode: do {

            // Set the name of the node (we will reference this later)
   = "callGC"

            // Default inits
            call_gc_node.text = "Send your HighScore of \(score) into Game Center"
            call_gc_node.fontSize = 25
            call_gc_node.position = CGPoint(

            // Self here is the instance (object) of our class, GameScene
            // This adds it to our view

        // Give our Add label some stuff
        initADDLabel: do {

            // Set the name of the node (we will reference this later)
   = "addGC"

            // Basic inits
            add_score_node.text = "ADD TO SCORE!"
            add_score_node.fontSize = 25
            add_score_node.position = call_gc_node.position

            // Align our label some
            add_score_node.runAction(SKAction.moveByX(0, y: 50, duration: 0.01))

            // Add it to the view


    override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
        for touch in touches {

            // Get the position of our click
            let TPOINT = touch.locationInNode(self)

            // Get the name (string) of the node that was touched
                node_that_was_touched: String?
                                                = nodeAtPoint(TPOINT).name

            // Prepare for switch statement, when we unwrap the optional, we don't want nil
            guard (node_that_was_touched != nil)
                else { print("-> before switch: found nil--not entering Switch");

            // Find out which node we clicked based on, then do stuff:
            switch node_that_was_touched! {

                case "callGC":
                    // We clicked the GC label:

                    GameOver: do {

                        print("GAME OVER!")

                        // If we have a high-score, send it to leaderboard:

                        // Reset our score (for the next playthrough)
                        score = 0

                        // Show us our stuff!

                case "addGC":
                    // we clicked the Add label:

                    // Update our *current score*
                    score += 1

                default: print("no matches found")



    override func update(currentTime: CFTimeInterval) {
        /* Called before each frame is rendered */
        call_gc_node.text = "Send your HighScore of \(score) into Game Center"


    // Gamecenter
    func gameCenterViewControllerDidFinish(gameCenterViewController: GKGameCenterViewController) {
        gameCenterViewController.dismissViewControllerAnimated(true, completion: nil)

    //shows leaderboard screen
    func showLeader() {
        let viewControllerVar = self.view?.window?.rootViewController
        let gKGCViewController = GKGameCenterViewController()
        gKGCViewController.gameCenterDelegate = self
        viewControllerVar?.presentViewController(gKGCViewController, animated: true, completion: nil)

    // Your "game over" function call
    func overrideHighestScore(gameScore: Int) {
        if gameScore > NSUserDefaults.standardUserDefaults().integerForKey("highscore")
            NSUserDefaults.standardUserDefaults().setInteger(gameScore, forKey: "highscore")


Pay special attention to

29: let my_leaderboard_id = "YOUR_LEADERBOARD_ID"

I put some silly ASCII art in there to make sure you don't miss it. You have to put in your actual leaderboard ID from the GameCenter set-up.

You have to add the GameCenter library as well, and do the iTunes connect to actually see your highscores in the pop-up window.

I think your initial problems were with not understanding some of the back-end of how SpriteKit and even iOS views work (which is totally fine, because Apple makes jumping in and making stuff very easy). But, as you see, following guides / tutorials can be difficult since your implementation will vary.

Here is some good info to start with:

Diagram of what happens each frame in SK:

enter image description here

So you see, the SKScene is the class with all of the fun stuff like Nodes and Actions, and is where everything (important to you) happens. You can generate these scenes through the Editor, but then you probably need to make a new .swift file to go with it (as each scene can have its own logic).

The editor is just a 'shortcut' to initializing a bunch of stuff, and honestly, you can make complete games with little code (but you very quickly find out that you want more)

So in this code, where you declare GameScene or PauseScreen (which are basically just class declarations, that inherit from SKScene), you quickly find this line talking about something that ISNT a scene:

override func didMoveToView(view: SKView) .. it's calling a SKView... what is that, and where did it come from?

(Read about SKView here, and look at its inheritance):

We find this SKView declaration in the GameViewController file, (which is just a class), notice that it's the same as the regular iOS apps mostly, as it inherits UIViewController:

override func viewDidLoad() {
    if let scene = GameScene(fileNamed:"GameScene") {
        // Configure the view.
        let skView = self.view as! SKView
        skView.showsFPS = true
        skView.showsNodeCount = true

        /* Sprite Kit applies additional optimizations to improve               rendering performance */
        skView.ignoresSiblingOrder = true

        /* Set the scale mode to scale to fit the window */
        scene.scaleMode = .AspectFill


Again, that method is declared in GameViewController.swift, which is basically just this: class GameViewController: UIViewController

So how does all of this relate to iOS apps and SpriteKit? Well, they are all mashed on top of each other:

IOS app anatomy:


Basically, from right to left, you have the Window, which is (correct me if wrong) the AppDelegate, then the ViewController, then your View, which has all of the cool stuff in it (Storyboards sit inside of the View, just as SKScenes sit inside of the View.... Labels, Nodes, or Buttons, all sit inside of their respective classes ((the view)))

It's all a big sandwich of inheritance.

Check out the Apple websites for more info.

Basically, everything is an Class inherited from a class inherited from a class and so on, so on... It can get messy. You can also see these inheritances in Xcode by CMD+clicking on them, which will jump you to the source file.

Goodluck with your studies and adventures in SpriteKit :)

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