Problem with removing a fixture and world event listeners

MikeHart · February 2012

Hi Atilim,

during a frame, I remove the fixture and the body of a sprite:

	local body = self.xBody
	local fixture = self.xFixture
	body:destroyFixture(fixture)
	world:destroyBody(body)

So far so good. The problem is, sometimes an event listener like onEndContact
fires with the destroyed fixture and so crashes with an error like this:

main.lua:885: Fixture is already destroyed.

The offending line here is

local bodyB = fixtureB:getBody()

Imho it happens when there are more than one contacts in a frame and after the first the fixture is destroyed. The event listener is added tot he world. Before firing an event, Gideros should check if one of the two fixtures are already destroyed and not call the event listener then.

Cheers
Michael

mykyl66 · February 2012

I had similar issues in the other language and ended up putting a gameActive = true while the game was active around certain functions. That meant when I was about to leave a game I would set the flag to false and nothing could fire and therefore be cleaned without errors.

No idea if that's clear enough or really what your talking about.

Mike

atilim · February 2012

@MikeHart That's a great catch! Currently, I set the fixture as destroyed, then call box2d's DestroyFixture function. But the order should be just the opposite. (first call DestroyFixture then set destroyed flag). Thank you.

@mykyl66 good tip

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