如何杀死SKScene

Question

I've got a game with a MasterViewController. It has a "Play" button that segues to the GameViewController. The GameViewController and GameScene are plain vanilla what a game build provides except I added an NSLog to the GameScene's update method and, on the storyboard, created a "Quit" button that segues back from the GameViewController to the MasterViewController.

Everything works as expected. I fire up the app and touch the Play button and it transitions to the GameViewController to the GameScene. Fine, I see the standard "Hello World" message and can touch to create spinning spaceships. I start getting the NSLog output from the update method. Great.

However, when I click the Quit button and it segues back to the MasterViewController, I am still getting the NSLog output from the GameScene update method so the GameScene is still active. I want the GameScene gone. Added a dealloc to the GameScene and it is never called, probably because of ARC.

In the GameViewController I added a weak gameScene property and:

- (void)viewWillDisappear:(BOOL)animated {
   [super viewWillDisappear:animated];
   NSLog(@"viewWillDisappear");
   [_gameScene removeAllChildren];
   [_gameScene removeAllActions];
   [_gameScene removeFromParent];
   _gameScene = nil;
}

Still getting the NSLog output from the GameScene update method. Sigh... How do I kill the GameScene dead, dead, dead?

I did the Play/Quit/Play/Quit transition several times. The output from the update method is:

2014-11-20 12:48:41.551 Demo[7386:2004098] update: 0x7b091090
2014-11-20 12:48:42.095 Demo[7386:2004098] update: 0x7ed21020
2014-11-20 12:48:42.656 Demo[7386:2004098] update: 0x7eb1c4b0
2014-11-20 12:48:43.217 Demo[7386:2004098] update: 0x7b091090
2014-11-20 12:48:43.762 Demo[7386:2004098] update: 0x7ed21020
2014-11-20 12:48:44.322 Demo[7386:2004098] update: 0x7eb1c4b0

So all of my GameScenes are still active in the background.

Answer 1

You must make sure no other objects are pointing strongly to the object you want to remove from memory. See Apple Developer .

Answer 2

I found a workaround - use a nav controller, which I alway hide to make room for my game. To transition to the next view controller in the hierarchy, use a "Show" segue. To pop back, add your own Back button and connect the action:

- (IBAction)backButtonClicked:(UIButton *)sender {
   [[self navigationController] popViewControllerAnimated:YES];
}

I also have one place in my GameViewController where I use a "Pause" button to pop all the way back to the root view controller.

- (IBAction)pauseButtonClicked:(UIButton *)sender {
   NSArray * viewControllers = self.navigationController.viewControllers;
   NSLog(@"nav view controllers: %@", viewControllers);
   UIViewController * targetViewController = viewControllers[0];
   NSLog(@"target controller: %@", targetViewController);
   [self.navigationController popToViewController:targetViewController animated:YES];
}

All this correctly deallocates the GameViewController and GameScene when they disappear.