Deallocate SKScene after modal transition - ios

Question

I have been creating a game in sprite kit using swift and have encountered a problem. I have two view controllers, each with one scene and one transitions to the other modally. This all works perfectly first time round, but then when i return to the first view controller and then go to the second again, i have using double the memory. This gives me the impression that nothing is being deallocated, but the objects are rather reallocated every time I transition to the scene. I ran the app in instruments and got the same result. In the below image i moved from one scene to the next, and then back to the first one again and yet it appears to reallocate the first scene and yet not clear any memory. As the dealloc method is unused now, i don't see how i can fix this. I will post the code to the first view controller below so you can have a look at it. Thanks a lot.
import UIKit
import SpriteKit
class SelectionViewController: UIViewController {
var selectionScene:SelectionScene?
var currentRocketName = ""
#IBOutlet var playButton: UIButton
override func viewDidLoad() {
super.viewDidLoad()
if let selectionScene = SelectionScene.unarchiveFromFile("SelectionScene") as? SelectionScene {
// Configure the view.
let skView = self.view as SKView
skView.showsFPS = true
skView.showsNodeCount = true
skView.multipleTouchEnabled = false
/* Sprite Kit applies additional optimizations to improve rendering performance */
skView.ignoresSiblingOrder = true
/* Set the scale mode to scale to fit the window */
selectionScene.scaleMode = .ResizeFill
selectionScene.viewController = self
skView.presentScene(selectionScene)
NSNotificationCenter.defaultCenter().addObserver(selectionScene, selector: "spinnerChanged", name: "spinnerValueChanged", object: nil)
NSNotificationCenter.defaultCenter().addObserver(selectionScene, selector: "productBought", name: "ProductBought", object: nil);
NSNotificationCenter.defaultCenter().addObserver(selectionScene, selector: "manageErrorInPurchase", name: "ErrorOccured", object: nil)
}
}
override func shouldAutorotate() -> Bool {
return true
}
override func viewDidAppear(animated: Bool) {
}
#IBAction func playButtonPressed(sender: UIButton) {
self.performSegueWithIdentifier("moveToGame", sender: nil)
}
override func prefersStatusBarHidden() -> Bool {
return true
}
override func supportedInterfaceOrientations() -> Int {
if UIDevice.currentDevice().userInterfaceIdiom == .Phone {
return Int(UIInterfaceOrientationMask.AllButUpsideDown.toRaw())
} else {
return Int(UIInterfaceOrientationMask.All.toRaw())
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Release any cached data, images, etc that aren't in use.
}
override func viewDidUnload() {
NSNotificationCenter.defaultCenter().removeObserver(selectionScene)
}
override func viewDidDisappear(animated: Bool) {
NSNotificationCenter.defaultCenter().removeObserver(selectionScene)
}
override func prepareForSegue(segue: UIStoryboardSegue!, sender: AnyObject!) {
if segue.identifier == "moveToGame" {
let destController = segue.destinationViewController as GameViewController
destController.rocketTexture = SKTexture(imageNamed: self.currentRocketName)
}
}
}
Both selectionScene and currentRocketName are passed to the viewController as soon as they are loaded into the view

Answer 1

I'm not familiar with Swift yet, so I'll give you examples in Objective-C.
Create an IBOutlet for skView. When you are going to present another ViewController, remove skView from it's superview and nil it out:
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
// Need to deallocate GameScene (if game is not paused)
[self.skView removeFromSuperview];
self.skView = nil;
....
}
Don't forget to add skView back to the ViewController's view, when ViewController is getting loaded:
if (!self.skView.window) {
[self.view addSubview:self.skView];
}
To easily check if SKScene was deallocated or not, add this method to it:
- (void)dealloc {
NSLog(#"GAME SCENE DEALLOCATED");
}

Answer 2

I had a similar issue.
Turns out I had created a strong reference by having an SKScene instance as a delegate in another class. After declaring each property of SKScene type or UIView type as weak my issue was resolved:
weak var skScene:SKScene!