实现CQRS时如何在控制器中获取创建的对象

Question

I am evaluating the CQRS pattern and wonder what would be the best way to obtain an Entity created by a command in the same action so I can render it in the view.

The two options I can think of are.

1) Create an id in the controller and send it with the command to fetch the entity by finding it by id. 2) Create an instance of the entity and send it with the command so I have a reference to it after it's populated

Example code

public function createEntityAction(array $data) {
    $eventDispatcher = $this->get('event_dispatcher');

    $eventDispatcher->dispatch(
        CreateEntityHandler::name, // Handler
        new Entity($data) // Command
    );

    // Placeholder //
      $entity = get-the-created-entity
    // // 

    return $this->view($entity, Response::HTTP_OK);    
}

Answer 1

Second option is not really an option. "Entity creation", which is in fact is a business operation, is a command handling.

Generally speaking, the one who sends a command, whose handler creates an entity, should send the entity id with it. In what way the identity is generated is just an implementation concern.

Usually, command handlers either do what they suppose to do and return nothing (or ACK) or throw (or NAK).