Creating the world

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
}

We begin by creating a variable...