Question

I have some body which grows. I added this body to the world.

...
someBody = world->CreateBody(&bodyDef);
someFixture = tapBody->CreateFixture(&someFixtureDef);
...

I think I do not need to paste all code here.

So I added body to the world. The question is how to change position, restitution… of the body which is already in the world? Am I allowed to do that here? (because I am getting errors when I try to change something in the tick method).

-(void) tick: (ccTime) dt
{
    world->Step(dt, velocityIterations, positionIterations);
    for (b2Body* b = world->GetBodyList(); b; b = b->GetNext())
    {

    }
}

Answer 1

Maybe instead of destroying and recreating the entire body you could accomplish what you need by destroying and creating a new fixture…

for (b2Body* b = world->GetBodyList(); b; b = b->GetNext())
{
    // This assumes you only have one fixture
    b2Fixture* f = b->GetFixtureList();
    f = f->GetNext();

    // Code here to create a new fixture/shape with different size (or whatever)

    // Destory old fixture and create new one
    b->DestoryFixture(f);
    b2Fixture* someFixture = b->CreateFixture(&someFixtureDef);

}

Sorry for any typos… haven’t tested any of this…