How to call a function in viewController from GameScene

Question

I am wanting to call a share function during game play. I have some code I can use in my GameViewController

func showTweetSheet() {
    let tweetSheet = SLComposeViewController(forServiceType: SLServiceTypeTwitter)
    tweetSheet.completionHandler = {
        result in
        switch result {
        case SLComposeViewControllerResult.Cancelled:
            //Add code to deal with it being cancelled
            break

        case SLComposeViewControllerResult.Done:
            //Add code here to deal with it being completed
            //Remember that dimissing the view is done for you, and sending the tweet to social media is automatic too. You could use this to give in game rewards?
            break
        }
    }

    tweetSheet.setInitialText("Test Twitter") //The default text in the tweet
    tweetSheet.addImage(UIImage(named: "TestImage.png")) //Add an image if you like?
    tweetSheet.addURL(NSURL(string: "http://twitter.com")) //A url which takes you into safari if tapped on

    self.presentViewController(tweetSheet, animated: false, completion: {
        //Optional completion statement
    })
}

I have also set the ViewController in my GameScene Class...

var viewController: GameViewController!

... and set the scene.viewController to self in my ViewController

class GameViewController: UIViewController {

override func viewDidLoad() {
    super.viewDidLoad()

    if let scene = GameScene.unarchiveFromFile("GameScene") as? GameScene {
        // Configure the view.
        let skView = self.view as! SKView
        skView.showsFPS = false
        skView.showsNodeCount = false

        /* 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

        skView.presentScene(scene)

        scene.viewController? = self

    }
}

However, When I call the function like so...

viewController.showTweetSheet()

... from my GameScene it gives me a "found nil when unwrapping an optional value" error.

I think I may need to set the scene.viewController to self later on, but I don't know how to do that in the viewController.

Any help would be much appreciated.

Answer 1

First of all, you don't need the question mark after scene.viewController. Second, scene.viewController = self should come before skView.presentScene(scene). This will probably fix your problem.

Lastly, it's considered bad design (or at least sloppy) to make an SKScene have a property that is a UIViewController. The scene class is now tied to using a UIViewController, and if you want to extend your code to something that doesn't use UIViewController to control views (e.g. you want to make a Mac version of your game), it won't work right away because it's hard-coded to work with UIViewController.

The "pure" way to do this would be a technique called "delegation" by iOS programmers. You create a protocol that will be your delegate, and make your view controller implement that protocol. Then the SKScene uses the protocol, not UIViewController.

All that said, you might want to leave out this complexity.