Runtime error - when using body:setActive

[obey]

Here is the part of the code that triggers the error (it is used for bullet collision with enemies):

Code: Select all

function beginContact(a, b, coll)
	if a:getCategory()==2 and b:getCategory()==2 then
		if a:getUserData() ~= b:getUserData() then
	    	a:getBody():setActive(false)-- This produces the error

When I comment out the line of the error, I get no error. What might cause this?

BTW:
I'm not uploading a love file because my game is relatively big (with plenty of assets).

[Plu]

What kind of runtime error?

[obey]

What kind of runtime error?

Attached image shows the exact error.

[Boolsheet]

This is an uncaught exception. It's fixed in 0.9.0, I think.

You're not supposed to change the world during an update/timestep. To my knowledge, setting a body active or inactive counts as that.

[obey]

This is an uncaught exception. It's fixed in 0.9.0, I think.

You're not supposed to change the world during an update/timestep. To my knowledge, setting a body active or inactive counts as that.

So how would you suggest to make the bullet disappear and the enemy's body to change to dead?
I need some kind of flag, and the active property sounded good for that.

[Boolsheet]

the active property sounded good for that.

Yeah, I wanted to use it like that too.

I guess you have to store the flag somewhere in a table. Haven't touched Box2D in quite a while and never did something big with it so I can't really go into the design of it, sorry..

[obey]

the active property sounded good for that.

Yeah, I wanted to use it like that too.

I guess you have to store the flag somewhere in a table. Haven't touched Box2D in quite a while and never did something big with it so I can't really go into the design of it, sorry..

Yea I thought about creating a table, but how would I know which object to flag out? the collisions are referencing the fixture (you can't attach user data on it), so even that doesn't help.
I need a property that Is bound to the fixture/body/shape that I can change in order to flag it out.

[Robin]

You can use a single table that is globally accessible and has the bodies as values:

Code: Select all

function beginContact(a, b, coll)
	if a:getCategory()==2 and b:getCategory()==2 then
		if a:getUserData() ~= b:getUserData() then
	    	inactive_bodies[#inactive_bodies + 1] = a:getBody()

in love.load:

Code: Select all

function love.load()
    -- ...
    inactive_bodies = {}
end

And in love.update:

Code: Select all

function love.update(dt)
    -- ...
    world:update(dt)
    for i, body in ipairs(inactive_bodies) do
        body:setActive(false)
    end
    inactive_bodies = {}
    -- ...
end

Hope that helps.

[obey]

You can use a single table that is globally accessible and has the bodies as values:

Code: Select all

function beginContact(a, b, coll)
	if a:getCategory()==2 and b:getCategory()==2 then
		if a:getUserData() ~= b:getUserData() then
	    	inactive_bodies[#inactive_bodies + 1] = a:getBody()

in love.load:

Code: Select all

function love.load()
    -- ...
    inactive_bodies = {}
end

And in love.update:

Code: Select all

function love.update(dt)
    -- ...
    world:update(dt)
    for i, body in ipairs(inactive_bodies) do
        body:setActive(false)
    end
    inactive_bodies = {}
    -- ...
end

Hope that helps.

Thanks,
I fixed it by using all these 3 :

Code: Select all

		zombies[i].fixture:setCategory(2) 
		zombies[i].fixture:setGroupIndex(3) --zombie group
		zombies[i].fixture:setUserData("1") --alive

And:

Code: Select all

function beginContact(a, b, coll)
	if a:getCategory()==2 and b:getCategory()==2 then
		if a:getGroupIndex() ~= b:getGroupIndex() then
	    	a:setUserData("0")
	    	b:setUserData("0")
	    end
    end
end