Question

I am writing an imagehandler for an engine. So far it’s going pretty good (I think) but I need help with deleting images. I have experience with vectors but not with maps.

The image handler has an std::map which has 2 elements:

std::map<std::string, SDL_Surface*> image_list_;
std::map<std::string, SDL_Surface*>::iterator it;

Then i have 2 methods in my ImageHandler class:

void AddImage(std::string/*file_name*/);
void DeleteImage(std::string/*file_name*/);

Here are the guts of these 2 methods:

bool ImageHandler::AddImage(std::string file_name)
{
    SDL_Surface* temp = NULL;
    if ((temp = Image::Load(file_name)) == NULL)
        return false;
    image_list_.insert(std::pair<std::string, SDL_Surface*>(file_name, temp));
    SDL_FreeSurface(temp);
    return true;
}

bool ImageHandler::DeleteImage(std::string file_name)
{
    if (image_list_.empty()) return;
    it = image_list_.find(file_name);
    if (!it) return false;
    image_list_.erase(it);
    return true;
}

I haven’t compiled this code so I am not aware of any syntax errors. If any exist you can just look past those.

I think my DeleteImage method will remove it from the map but to avoid memory leaks when it loads an image I need to do this:

SDL_FreeSurface(SDL_Surface*);

So I think I need to access an iterator’s second element at a specific map index. Am I doing it right so far and how would I be able to do this?

Answer 1

Like this:

bool ImageHandler::DeleteImage(std::string const & file_name)
{
  if ((it = image_list_.find(file_name)) == image_list_.end())
  {
    return false;
  }

  SDL_FreeSurface(it->second);
  image_list_.erase(it);
  return true;
}