Question

I am trying to write an iPhone game using cocos2d and Box2D, which means I have to mix between Objective-C and C++. I have a question regarding using pointers to objects of gameLevels and levelObjects that I have created.

I have a class called GameLevel which contains a vector of levelObjects. I thought that using pointers was the way to do it, to make sure I use as little memory as possible. That means that my vector is

std::vector<LevelObject*>* levelObjects;

The LevelObject class contains the sprite, b2bodyDef and so on, all pointers as well.

The problems started when I wanted to iterate through this vector when I wanted to draw a level. The code I wrote was this:

-(void)startLevel:(b2World*) world withLevel:(GameLevel*) level{
std::vector<LevelObject*>::iterator it;
for (it = level->getLevelObjects()->begin() ; it != level->getLevelObjects()->end(); ++it) {
    CCSprite* sprite = it->sprite; //Here XCode complaints about "Member reference base type 'LevelObject *' is not a structure or union" and "Use of undeclared identifier 'sprite'". I cannot seem to access any of the objects variables/methods from it->

So the question I ask is: Is this a good way to to this, with a pointer to vector of pointers? And why doesn’t the iteration work?

Thanks 🙂

EDIT: getLevelObjects() are:

std::vector<LevelObject*>* getLevelObjects(){return levelObjects;}

Answer 1

Your iterators point to pointers, so you need two dereferences:

(*it)->sprite

the dereference of the iterator,

*it

gives you a LevelObject*.