saving contact bodies to be destroyed - cocos2d-iphone

Question

In my code I would like to destroy one of two contacted bodies. Within the beginContact the following method in CCPhysicsSprite is called:
-(void)contactMade:(CCPhysicsSprite*)contactedSprite {
int spriteTag1 = self.tag;
int spriteTag2 = contactedSprite.tag;
if (((spriteTag1 == 3) && (spriteTag2 == 4)) || ((spriteTag1 == 4) && (spriteTag2 == 3)) {
CCPhysicsSprite* heroSprite = (CCPhysicsSprite*)[self getChildByTag:4];
b2World* world;
world->DestroyBody(heroSprite.b2Body);
heroSprite.b2Body = NULL;
[heroSprite.parent removeChild:heroSprite];
}
I get a signal SIGABRT pointing to
b2Assert(m_bodyCount > 0);
After searching on this issue. I read that the contact body has to be saved and destroyed after the timestep. How can I do this, given that I have set my contact conditions in the CCPhyscisSprite.

Answer 1

You can add a flag ( like : isDead ... ) to your physical object and in collision event just change that flag value to TRUE .
-(void) CollisionBegin:(b2Fixture*)target With:(b2Fixture*) source
{
if ( target->GetBody()->GetType() == b2_dynamicBody)
{
yourCustomClass *temp = (yourCustomClass *)target->GetBody()->GetUserData();
temp->isDead = true ;
}
}
Then in update function after step get all physical world's object and find that specific object by flag ( Here : isDead ) , and destroy that .
-(void) update: (ccTime) dt
{
int32 velocityIterations = 8;
int32 positionIterations = 3;
world->Step(dt, velocityIterations, positionIterations);
// remove your box2d object here , after step function
for ( b2Body *b = world->GetBodyList(); b; )
{
b2Body *baba = b->GetNext();
if ( b->GetUserData() != NULL && b->GetType() == b2_dynamicBody)
{
yourCustomClass *t = (yourCustomClass *)b->GetUserData();
if ( t->isDead )
{
world->DestroyBody(b); // remove physical body
[self removeChild:t]; // remove node from super layer
}
}
b = baba ;
}
}