Command Bus

The Command Bus implements the Command Query Responsibility Segregation (CQRS) pattern for handling commands. Commands represent intentions to modify state and are handled by registered handlers.

Example: User Management Commands

import {
  Command,
  HybridCommandBus,
  type CommandHandlerInterface,
} from "@dxbox/use-less-react/classes";

// Define command payload
interface CreateUserPayload {
  email: string;
  name: string;
  password: string;
}

// Create command class
class CreateUserCommand extends Command<"CreateUser", CreateUserPayload> {
  get type(): "CreateUser" {
    return "CreateUser";
  }
}

// Define command handler
class CreateUserHandler implements CommandHandlerInterface<CreateUserCommand> {
  async handle(command: CreateUserCommand): Promise<void> {
    const { email, name, password } = command.payload;

    // Perform the command action (e.g., save to database)
    await this.userRepository.create({
      email,
      name,
      password: await this.hashPassword(password),
    });

    // Optionally publish events after command execution
    await this.eventBus.publish(
      new UserCreatedEvent({ userId: command.id, email })
    );
  }

  constructor(
    private userRepository: UserRepository,
    private eventBus: EventBus
  ) {}
}

// Setup command bus
const commandBus = new HybridCommandBus({
  monitoringService: myMonitoringService,
});

// Register handler
commandBus.registerLocalHandler("CreateUser", new CreateUserHandler(...));

// Dispatch command
const command = new CreateUserCommand({
  email: "user@example.com",
  name: "John Doe",
  password: "secure123",
});

await commandBus.dispatch(command);

API

HybridCommandBus

• registerLocalHandler<T>(commandType: T["type"], handler: CommandHandlerInterface<T>): void - Register a handler for a command type
• dispatch(command: UntypedCommandType): Promise<void> - Dispatch a command to its handler

Command

• id: string - Unique command identifier (optional, gets default value)
• timestamp: Date - Command creation timestamp (optional, gets default value)
• type: TType - Command type (must be implemented by subclass)
• payload: TPayload - Command payload data

CommandHandlerInterface

• handle(command: TCommand): Promise<void> - Handle the command