CODEWITHSUNDEEP
iosswiftsprite-kitskscene
Confused
Confused

Reputation: 6288

Children of a Scene not releasing fast enough?

Have a couple of child nodes in a scene, and do a quick transition to a new scene.

In the new scene, didMove(to view: ….) is used to add the children from the previous scene to this next scene.

SceneKit crashes when doing this quickly, seemingly because the children of the old scene haven’t yet been released.

If I add a slight delay before adding the children to the second scene, it’s fine… it seems SpriteKit isn’t releasing the child fast enough for the scene transition.

the above is the most important thing to understand with regard the purpose for this question. I (wrongly) assumed SpriteKit would make sure all nodes attached to a scene were released before attempting to add them to a subsequent scene. It doesn't do this. But it does release them, it just takes a little time. Is this one frame? One second? Dunno...

My scene transition time is 0.25 seconds

Also tried using willMove(to view: ….) in the original scene to manually remove the children. This also doesn’t work, seemingly same behaviour: not fast enough.

Also tried assuming the child still has a relationship to its parent, so tried moving to its new parent, the new scene, with move(toParent:…) this also crashes. So maybe the children are already flagged as about to be released, I suppose.

Is this known about, and if so, how is it dealt with?

Upvotes: 3

Views: 124

Answers (2)

Confused
Confused

Reputation: 6288

“Is this a known about, and if so, how is it dealt with?"

Yes, this is a known issue of the SceneKit and IOS design and operational paradigms. It is considered that a scene must always be present and upon the screen. Can't have time without a scene onscreen.

As a result, for a brief time during transitions, both scenes are loaded, and active.

There are three ways to do deal with this problem:

  • Remove all content from the old scene prior to executing the transition so it can be instantly loaded by the new scene in didMove(to view...

    or

  • Wait for completion of the transition before loading any content from the old scene into the new scene so there's no ownership conflicts of children.

    or

  • KnightOfDragon’s first suggestion to use .copy() so there’s not the same instances being fought over by the scenes.

Upvotes: 0

Fluidity
Fluidity

Reputation: 3995

You can't present a scene and have willMove function at the same time in the same frame (SK loop)--your next scene's viewDidLoad will be called before the previous scene is destroyed. You have to remove all of the nodes before calling presentScene:

I suggest making a global variable of some sort to access your SKView; with that you can have control over your scenes from anywhere:

currentScene.removeAllChildren()
gView!.presentScene(nextScene)

Upvotes: 2

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