Losing reference to GameViewController from inside SpriteKit when moving between scenes - want to move between SKScene and UITableView

Question

I have a simple (multi scene) spritekit game and would like to implement and display a settings screen using a UITableViewContoller. I am close but keep losing my reference to the games view controller when i change scene, which means i can only segue to the UITableViewController on the first scene when my game starts. I'm hoping someone can help. I setup the UITableView in the storyboard and setup a segue to the tableview from my GameViewController in there.

I have the following set up in my GameViewController file:

override func viewDidLoad() {
    super.viewDidLoad()

    if let view = self.view as! SKView? {
        // Load the SKScene
        if let scene = SKScene(fileNamed: "MenuScene") {
            // Set the scale mode to scale to fit the window
            scene.scaleMode = .aspectFill

            //I'VE ADDED THIS
            if let gameScene = scene as? MenuScene {
                gameScene.viewController = self
            }
            // Present the scene
            view.presentScene(scene)
        }

        view.ignoresSiblingOrder = true
    }
}

func showSettings() {
    performSegue(withIdentifier: "openSettings", sender: self)
}

which gives me a reference to the GameViewController from my SKScene. I then load the UITableViewController from my SKScene in spritekit when a user touches an SKLabelNode. A simpler version of my MenuScene code looks something like this:

class MenuScene: SKScene {
var viewController: GameViewController?

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?)
{
    let touch:UITouch = touches.first!
    let positionInScene = touch.location(in: self)
    let touchedNode = self.atPoint(positionInScene)

    if let name = touchedNode.name
    {
        let transition:SKTransition = SKTransition.fade(withDuration: 0.75)
        var scene:SKScene = SKScene()

        if (name == "settingsBTN"){
            viewController?.showSettings()
        }
        else if (name == "randomBTN"){
            scene = StarScene(size: self.size)
            scene.backgroundColor = SKColor.black
            self.view?.presentScene(scene, transition: transition)
        }
    }
}

}//end of MenuScene

The table view is presented fine when i tap the settingsBTN when first starting the game. however, if i visit another scene in my game (e.g. by pressing randomBTN) and return back to the menu scene i can no longer segue to the Settings view as i have lost the reference to the viewcontroller (it shows as nil) so i can't call the showSettings method in the GameViewController that performs the segue (presumably because i set up the reference to the view controller in the view controller itself).

I can't figure out how to maintain the reference to my GameViewController so i can present the settings screen at any point. Please could someone help.

Alexandru Vasiliu Alexandru Vasiliu · Accepted Answer · 2019-12-23T20:52:04

There are two simple methods to call a GameViewController function from other classes: through a delegate or by making the class instance static.

// DELEGATE
//
// GameViewController.swift

protocol GameView_Delegate
{
    func show_ui()
}

class GameViewController: UIViewController, GameView_Delegate
{
    override func viewDidLoad()
    {

        //   ... 

        if let view = self.view as! SKView?
        {
            if let scene = SKScene(fileNamed: "MenuScene")
            {        
                scene.scaleMode = .aspectFill

                // pass GameViewController reference
                scene.gv_delegate = self
            }

            view.presentScene(scene)
         }

        // ...

    }

    func show_ui()
    {
        // show ui
        // ...
    }
}

// MenuScene.swift

class MenuScene: SKScene
{
    var gv_delegate : GameView_Delegate!

    func settings()
    {
        // call function show_ui from GameViewController
        gv_delegate.show_ui()
    }

    func game_scene()
    {
        let transition = SKTransition.fade(with: UIColor.white, duration: 1.0)
        let next_scene = GameScene()
        next_scene.anchorPoint = CGPoint(x: 0.5, y: 0.5)
        next_scene.scaleMode = self.scaleMode
        next_scene.size = self.size

        // before moving to next scene, we must pass the delegate, so we
        // don't  lose the connection with the GameViewController
        next_scene.gv_delegate = gv_delegate
        self.view?.presentScene(next_scene, transition: transition)
    }
}

// GameScene.swift

class GameScene: SKScene
{
    var gv_delegate : GameView_Delegate!

    func settings()
    {
        // call function show_ui from GameViewController
        gv_delegate.show_ui()
    }

    func main_scene()
    {
        let transition = SKTransition.fade(with: UIColor.white, duration: 1.0)
        let next_scene = MainScene()
        next_scene.anchorPoint = CGPoint(x: 0.5, y: 0.5)
        next_scene.scaleMode = self.scaleMode
        next_scene.size = self.size

        // before moving to next scene, we must pass the delegate, so we
        // don't lose the connection with the GameViewController
        next_scene.gv_delegate = gv_delegate
        self.view?.presentScene(next_scene, transition: transition)
    }
}

When you enter a new scene, for example GameScene, the old scene MainScene in our case is deallocated (all variables emptied, all references destroyed) and a new GameScene instance is created and displayed on screen. If afterwards you want to exit that scene and enter MainScene, a new instance of that class will be created with the GameViewController reference empty. We should reference it again or pass the reference before exiting the scene (as in my example).

// STATIC
//
// GameViewController.swift

class GameViewController: UIViewController
{
    static var shared : GameViewController!

    override func viewDidLoad()
    {
        super.viewDidLoad()

        GameViewController.shared = self

        // ...

    }

    func show_ui()
    {
        // show ui
        // ...
    }
}


// MenuScene.swift

class MenuScene: SKScene
{
    func settings()
    {
        // call function show_ui from GameViewController

        GameViewController.shared.show_ui()
    }
}

Read pros/cons of each method and chose the one that suits your app the best. Also, avoid using UIKit inside SpriteKit.

Losing reference to GameViewController from inside SpriteKit when moving between scenes - want to move between SKScene and UITableView

1 Answers