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The Command Pattern

Why?

  • Models (@colyseus/schema) should contain only data, without game logic.
  • Rooms should have as little code as possible, and forward actions to other structures

The command pattern has several advantages, such as:

  • It decouples the classes that invoke the operation from the object that knows how to execute the operation.
  • It allows you to create a sequence of commands by providing a queue system.
  • Implementing extensions to add a new command is easy and can be done without changing the existing code.
  • Have strict control over how and when commands are invoked.
  • The code is easier to use, understand and test since the commands simplify the code.

Usage

Installation

npm install --save @colyseus/command

Initialize the dispatcher in your room implementation:

import { Room } from "colyseus";
import { Dispatcher } from "@colyseus/command";

import { OnJoinCommand } from "./OnJoinCommand";

class MyRoom extends Room<YourState> {
  dispatcher = new Dispatcher(this);

  onCreate() {
    this.setState(new YourState());
  }

  onJoin(client, options) {
    this.dispatcher.dispatch(new OnJoinCommand(), {
        sessionId: client.sessionId
    });
  }

  onDispose() {
    this.dispatcher.stop();
  }
}

const colyseus = require("colyseus");
const command = require("@colyseus/command");

const OnJoinCommand = require("./OnJoinCommand");

class MyRoom extends colyseus.Room {

  onCreate() {
    this.dispatcher = new command.Dispatcher(this);
    this.setState(new YourState());
  }

  onJoin(client, options) {
    this.dispatcher.dispatch(new OnJoinCommand(), {
        sessionId: client.sessionId
    });
  }

  onDispose() {
    this.dispatcher.stop();
  }
}

How a command implementation looks like:

// OnJoinCommand.ts
import { Command } from "@colyseus/command";

export class OnJoinCommand extends Command<YourState, {
    sessionId: string
}> {

  execute({ sessionId }) {
    this.state.players[sessionId] = new Player();
  }

}

// OnJoinCommand.js
const command = require("@colyseus/command");

exports.OnJoinCommand = class OnJoinCommand extends command.Command {

  execute({ sessionId }) {
    this.state.players[sessionId] = new Player();
  }

}

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