The first object of Box2D that you will create is the world that holds the simulation itself. In addition to the world, you will also create a few other things in the CreateWorld function from the GameWorld.cpp file:
void GameWorld::CreateWorld()
{
// create world
b2Vec2 gravity;
gravity.Set(0, -10.0f);
world_ = new b2World(gravity);
// tell world we want to listen for collisions
world_->SetContactListener(this);
// create the moving container that will hold all the game elements
game_object_layer_ = CCNode::create();
addChild(game_object_layer_, E_LAYER_FOREGROUND);
#ifdef ENABLE_DEBUG_DRAW
debug_draw_ = new GLESDebugDraw(PTM_RATIO);
world_->SetDebugDraw(debug_draw_);
uint32 flags = 0;
flags += b2Draw::e_shapeBit;
// flags += b2Draw::e_jointBit;
// flags += b2Draw::e_aabbBit;
// flags += b2Draw::e_pairBit;
// flags += b2Draw::e_centerOfMassBit;
debug_draw_->SetFlags(flags);
#endif
}