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CQRS

CQRS stands for Command Query Responsibility Segregation It states that every method should either be a command that performs an action, or a query that returns data to the caller, but not both.

Commands & CommandHandlers​

The skeleton allows you to use commands and command handlers to perform actions. These 2 always come in pairs, when creating a new command in the write model, a corresponding command handler has to be created as well.

Creating a new command​

It's considered best practice to create a new namespace for every new command you create. This allows you to "bundle" each action (Command + CommandHandler).

CreateUser.php
namespace App\Domain\WriteModel\User\CreateUser;

class CreateUser extends DomainCommand
{
 
}

Creating the corresponding command handler​

Then create a corresponding command handler in the same namespace. Make sure that you

  • Add the AsCommandHandler attribute to it
  • The class name is NameOfTheEvent + CommandHandler.
CreateUserCommandHandler.php
namespace App\Domain\WriteModel\User\CreateUser;

#[AsCommandHandler]
class CreateUserCommandHandler implements CommandHandler
{
    public function __construct(
    ) {
    }

    public function handle(DomainCommand $command): void
    {
        assert($command instanceof CreateUser);

        // Do stuff.
    }
}

Using the CommandBus​

The CommandBus allows you to dispatch (=sync) commands. Just inject it into your service and call the dispatch() method. It will then magically 🧙‍ call the handle() method on the corresponding command handler.

class SomeService
{
    public function __construct(
    ) {
         private readonly CommandBus $commandBus,
    }

    public function someMethod(): void
    {
        $this->commandBus->dispatch(new CreateUser(/*...*/));
    }
}