CommandBus

The CommandBus handles commands (mutations/actions) in a CQRS architecture.

Class Definition

class CommandBus implements CommandBusInterface {
  constructor(props?: CommandBusConstructorProps);
  
  dispatch<TCommand extends UntypedCommandType>(
    command: TCommand
  ): Promise<void>;
  
  register<TCommand extends UntypedCommandType>(
    handler: CommandHandlerInterface<TCommand>
  ): void;
}

Constructor

new CommandBus(props?: CommandBusConstructorProps)

Creates a new CommandBus instance.

Parameters:

• props?: CommandBusConstructorProps - Optional configuration

  interface CommandBusConstructorProps {
    remoteSender?: RemoteCommandSenderInterface | null;
    monitoringService?: MonitoringService | null;
  }

Example:

const commandBus = new CommandBus();
// or with options
const commandBus = new CommandBus({
  remoteSender: myRemoteSender,
  monitoringService: myMonitoringService,
});

Methods

register<TCommand>(handler: CommandHandlerInterface<TCommand>): void

Registers a command handler.

Type Parameters:

• TCommand - The command type (must extend UntypedCommandType)

Parameters:

• handler: CommandHandlerInterface<TCommand> - The handler function

  interface CommandHandlerInterface<TCommand extends UntypedCommandType> {
    (command: TCommand): Promise<void>;
  }

Example:

commandBus.register(async (command: CreateTodoCommand) => {
  // Handle command
  await todosRepository.create(command.payload);
});

dispatch<TCommand>(command: TCommand): Promise<void>

Dispatches a command to registered handlers.

Type Parameters:

• TCommand - The command type

Parameters:

• command: TCommand - The command to dispatch

Returns: Promise<void> - Resolves when the command is handled

Example:

const command = new CreateTodoCommand({ text: "Learn xndr" });
await commandBus.dispatch(command);

Interface

interface CommandBusInterface {
  dispatch<TCommand extends UntypedCommandType>(
    command: TCommand
  ): Promise<void>;
  
  register<TCommand extends UntypedCommandType>(
    handler: CommandHandlerInterface<TCommand>
  ): void;
}