component architecture

main.cpp

/* In this model, the actor owns a bunch of components, which in turn 
serves as the base class for the component interfaces. Whenever a
system needs access to a component, it asks the actor for that interface
and gets a pointer to the appropriate interface object. */

struct Component
{

};

struct AiComponent: public Component
{

};

struct HumanAiComponent: public AiComponent
{

};

struct DrawComponent: public Component
{

};

struct Actor
{
  ~Actor()
  {
    for (auto c : components) delete component;
  }
  std::map<std::string, Component*> components;
};

struct ActorFactory
{
  Actor* create(const char* fileName)
  {
    std::ifstream f(fileName);
    std::string line;
    Actor* pActor = new Actor;
    
    while (std::getline(f, line))
    {
      if (line == "human_ai")
        pActor.components["ai"] = new HumanAiComponent;
      if (line == "zombie_ai")
        pActor.components["ai"] = new HumanAiComponent;
      if (line == "draw")
        pActor.components["draw"] = new DrawComponent;
    }
    return pActor;
  }
};

struct System
{
  void think(Actor a)
  {
    AiComponent* ac = a.components["ai"];
    if (ac) ac->think(a);
  }
  void draw(Actor a)
  {
    DrawComponent* dc = a.components["draw"];
    if (dc) dc->draw(a);
  }
}

int main()
{
  ActorFactory af;
  std::list<Actor*> actors;
  actors.push_back(af.create("human.txt"));
  actors.push_back(af.create("zombie.txt"));
  
  System s;
  for (auto actor : actors)
  {
    s.think(actor);
    s.draw(actor);
  }
  
  for (auto actor : actors) delete actor;
}