BlacksmithProject - CommandBus

Why ?

In order to improve my skills, I'm doing my own implementation of a CommandBus.

Installation

composer require blacksmith-project/command-bus

How to set it up?

• Your handlers need to
  • be callable (implements an __invoke() method).
  • be named after the command they handle:

    $command = new AddSugarToCoffee();
    $handler = new AddSugarToCoffeeHandler();

• Handlers must be added to a CommandHandlerMap:

  $map = new SimpleCommandHandlerMap([$handler, $anotherHandler]);
  $map->add($yetAnotherHandler);

• Your CommandBus takes as parameter a CommandHandlerMap.

How to do this in Symfony ?

1. Declare your Handlers as a Service.
2. Tag them with a specific tag such as my_app.command_handler.
3. Declare your CommandHandlerMap as a Service.
4. Make it use the tagged my_app.command_handler services as arguments.
5. Declare your CommandBus as a Service.
6. Make it use the CommandHandlerMap as argument.

Example:

    # config/services.yaml

    ############
    # Commands #
    ############
    MyApp\Domain\ACommandHandler:
        tags:
            - 'my_app.command_handler'
    
    MyApp\Domain\AnothenCommandHandler:
        tags:
            - 'my_app.command_handler'

    ########################
    # CommandHandlerMapper #
    ########################
    BSP\CommandBus\SimpleCommandHandlerMap:
        arguments: [!tagged my_app.command_handler]

    ##############
    # CommandBus #
    ##############
    BSP\CommandBus\SimpleCommandBus:
        arguments:
            - BSP\CommandBus\SimpleCommandHandlerMap

How to use it?

Now, you only need to inject your CommandBus and execute commands.

Example:

public function __construct(CommandBus $commandBus)
{
    $this->commandBus = $commandBus;
}

public function doSomethingFromCLI(): void
{
    $command = new DoSomething('please');

    $this->commandBus->execute($command);

    $output->writeln('command has been executed.');
}