How to group generic classes?

Question

I am working on a generic game engine for simple board games and such. I am defining interfaces that I will require each game to implement I have classes like IGame, IGameState, IBoardEvaluator, and IMove.

I have methods like IGame.PerformMove(IMove move), that I would like to restrict. If I am playing tic-tac-toe I would like to enforce that I can only use the concrete classes TTTGame, TTTState, TTTMove, etc...

I can think of several ways to do this, but none of them sound fun. Maybe all classes could have a single generic parameter, and I could make sure it matches.

so IGame<T> has method PerformMove(IMove<T> move)

If that works out, I wouldn't know what class to use for T. Maybe it doesn't matter.

My other idea is put a bunch of generic parameters on IGame and give it all of the classes I need. So I would create class TTTGame<TTTMove,TTTState,TTTMove....>

That isn't pretty either. Is there a common pattern to do this?

Answer 1

The whole point of interfaces is to not care about the concrete implementation of the class. Hence I don't see a need to directly enforce only a certain class, in that case an argument could be made to just pass the class itself.

Such as

TTTGame : IGame 
{
    PerformMove(TTTMove move);
}

Perhaps this is what you are talking about.

public interface IGame<T> where T:IMove
    {
        void PerformMove(T move);
    }

public class TTTGame : IGame<TTTMove>
    {

        public void PerformMove(TTTMove move)
        {
            //perform move
        }

    }

Now your IGame is forced to take an IMove, but like you said..with more classes like (IState..etc) this will get messy quick.

Answer 2

I dont see what advantage you get from specifying that your TTTGame class can only take TTTMoves.

I think you might be over engineering here.

The only thing you are protecting yourself from by doing that is some rogue MonopolyMove class becoming self-aware and putting itself in your code.

I say stick with the interface definitions and avoid the generics unless you have a really valid case. I dont see one based on what you have mentioned.

Answer 3

I'd say that the fact that you're feeling a need to restrict the implementation of your interfaces to certain classes is an indication of the interfaces not being specific enough.

Is IGame really a good idea in the first place? The name indicates that it could be equally valid for tic-tac-toe and Quake. Sure, there are some similarities between different board games (such as performing moves), but will you really benefit from creating an abstraction at that high level?