Simple Cocos2d Box2d Action On Collision

I have been looking for weeks for an OBJ-C based tutorial on how to call a method when a specific b2body collides with something else (not everything).

Basically, a block falls to the ground every second. This works fine, but when it hits the ground or the player, the 开发者_如何学Goblock should get deleted and pieces of it (different object) should be spawned.

Can anyone tell me how to do this?

Any help would be hot

Thanks

I think this is the one that you need..You need to include MycontactListener

-(void) checkForHit{

std::vector<b2Body *>toDestroy;

std::vector<MyContact>::iterator pos;

for(pos = _contactListener->_contacts.begin(); pos != _contactListener->_contacts.end(); ++pos) {

MyContact contact = *pos;

bodyA = contact.fixtureA->GetBody();

bodyB = contact.fixtureB->GetBody();

if (bodyA->GetUserData() != NULL && bodyB->GetUserData() != NULL) {

spriteA = (CCSprite *) bodyA->GetUserData();

spriteB = (CCSprite *) bodyB->GetUserData();

//NSLog(@”sprite tag is  %d”,spriteA.tag);

if (spriteA.tag == 50)  {

if (std::find(toDestroy.begin(), toDestroy.end(), bodyB) == toDestroy.end()) {

toDestroy.push_back(bodyB);
}

}

std::vector<b2Body *>::iterator pos2;
for(pos2 = toDestroy.begin(); pos2 != toDestroy.end(); ++pos2) {
b2Body *body = *pos2;
if (body->GetUserData() != NULL) {
CCSprite *sprite = (CCSprite *) body->GetUserData();
[self removeChild:sprite cleanup:YES];
}
_world->DestroyBody(body);
}

or if you dont't want to use contact listener.you can create a fixture for ground body and a body that u want to destroy and use the following code to check if it is intersecting and destroy it...

if((contact.fixtureA == groundFixture && contact.fixtureB == bodyFixture) ||
    (contact.fixtureA == bodyFixture&& contact.fixtureB == groundFixture ))
    {
    //destroy the body
    }

I have realized that as my object fall to the ground, i could create my own VERY simple physics by creating a start velocity, and then increasing it in the update method by a specific amount.

For the collision, my objects all fit in a 48pt wide grid so i could do simple rectangular collision detection.