Question

class Game {
  public:
    void draw_string(const char *text, int x, int y, TTF_Font *font, SDL_Color color, bool center);

  private:
    void spawn_enemies(vector <Enemy*>& enemies);
};

I have that as the definition of a class, and the definition of spawn_enemies is as follows:

void Game::spawn_enemies(vector <Enemy*>& enemies) {
  if (rand() % difficulty == 0) {
    Enemy *enemy = new Enemy(screen, zombie_image);
    enemies.push_back(enemy);
  }
}

And then I call spawn_enemies:

game.spawn_enemies(enemies);

And I define enemies as:

vector<Enemy*> enemies;

Any idea of why I get this error:

error: no matching function for call to ‘Game::spawn_enemies(std::vector<Enemy*>&)’            
note: candidate is:
note: void Game::spawn_enemies(int)
note:   no known conversion for argument 1 from ‘std::vector<Enemy*>’ to ‘int’

Answer 1

I wasn’t doing “using namespace std;” on the header file, so it wasn’t
including vector, which was causing a lot of weird mistakes

This is why it is good to use std:: instead of using namespace std.
It makes your code easier to understand and your code will still compile if they ever add Game or Enemy to the STL (Unlikely, I know). And it would allow you to add your own version of vector, min/max etc. if you really wanted to (I wouldn’t recommend it though).