How to design the relation between a Game and a Player in a game?

Question

I am currently attempting to make a Trading Card Game and I have got a whole array of features working already, yet I am stuck now at the portion where one player can attacker another player (more strictly: the monster cards of another player on the field). The game is designed primarely to be played with two players in mind, though having it open for future extensions is never a bad idea.

This is the design I have so far, shown as a minimalistic example in pseudo-code:

class Game
    private final Player self
    private final Player opponent

class Player
    private final String name
    ...

The game loops over all players and lets them do their turn, which may involve attacking another player. That method has the following structure:

class AttackMonsterAction
    private final int monsterIndex
    private final int targetMonsterIndex
    private final Player targetPlayer

    public void performAction(final Player player)

If it is of any relevance, I am coding this in Java.

My concrete question is the following: How do I create my class design such that AttackMonsterAction called from a certain Player object, can reference "the other player"?

Answer 1

A couple of options come to mind:

• Pass a GameState object to performAction, the GameState represents the current environment including the other palyer(s) and game board. This would allow you to move performAction into an interface and use it for your other actions such as move and hide

• Use a Mediator Object 2 to manage the interaction between the two players.

Regarding adding more players in the future; sounds like a big redesign so apply the XP principal of "You aren't gonna need it " and dont add it yet. Write tests to prove that the game works and then when you want to add more players use you tests to make sure that the two player game still works.