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124 changes: 56 additions & 68 deletions messenger/handler_results.rst
Original file line number Diff line number Diff line change
Expand Up @@ -6,23 +6,19 @@ Getting Results from your Handler

When a message is handled, the :class:`Symfony\\Component\\Messenger\\Middleware\\HandleMessageMiddleware`
adds a :class:`Symfony\\Component\\Messenger\\Stamp\\HandledStamp` for each object that handled the message.
You can use this to get the value returned by the handler(s):
You can use this to get the value returned by the handler(s)::

.. configuration-block::
use Symfony\Component\Messenger\MessageBusInterface;
use Symfony\Component\Messenger\Stamp\HandledStamp;

.. code-block:: php
$envelope = $messageBus->dispatch(SomeMessage());

use Symfony\Component\Messenger\MessageBusInterface;
use Symfony\Component\Messenger\Stamp\HandledStamp;
// get the value that was returned by the last message handler
$handledStamp = $envelope->last(HandledStamp::class);
$handledStamp->getResult();

$envelope = $messageBus->dispatch(SomeMessage());

// get the value that was returned by the last message handler
$handledStamp = $envelope->last(HandledStamp::class);
$handledStamp->getResult();

// or get info about all of handlers
$handledStamps = $envelope->all(HandledStamp::class);
// or get info about all of handlers
$handledStamps = $envelope->all(HandledStamp::class);

A :class:`Symfony\\Component\\Messenger\\HandleTrait` also exists in order to ease
leveraging a Messenger bus for synchronous needs.
Expand All @@ -41,77 +37,69 @@ As queries are usually synchronous and expected to be handled once,
getting the result from the handler is a common need.

To make this easy, you can leverage the ``HandleTrait`` in any class that has
a ``$messageBus`` property:
a ``$messageBus`` property::

// src/Action/ListItems.php
namespace App\Action;

.. configuration-block::
use App\Message\ListItemsQuery;
use App\MessageHandler\ListItemsQueryResult;
use Symfony\Component\Messenger\HandleTrait;
use Symfony\Component\Messenger\MessageBusInterface;

.. code-block:: php
class ListItems
{
use HandleTrait;

public function __construct(MessageBusInterface $messageBus)
{
$this->messageBus = $messageBus;
}

// src/Action/ListItems.php
namespace App\Action;
public function __invoke()
{
$result = $this->query(new ListItemsQuery(/* ... */));

use App\Message\ListItemsQuery;
use App\MessageHandler\ListItemsQueryResult;
use Symfony\Component\Messenger\HandleTrait;
use Symfony\Component\Messenger\MessageBusInterface;
// Do something with the result
// ...
}

class ListItems
// Creating such a method is optional, but allows type-hinting the result
private function query(ListItemsQuery $query): ListItemsResult
{
use HandleTrait;

public function __construct(MessageBusInterface $messageBus)
{
$this->messageBus = $messageBus;
}

public function __invoke()
{
$result = $this->query(new ListItemsQuery(/* ... */));

// Do something with the result
// ...
}

// Creating such a method is optional, but allows type-hinting the result
private function query(ListItemsQuery $query): ListItemsResult
{
return $this->handle($query);
}
return $this->handle($query);
}
}

Hence, you can use the trait to create command & query bus classes.
For example, you could create a special ``QueryBus`` class and inject it
wherever you need a query bus behavior instead of the ``MessageBusInterface``:
wherever you need a query bus behavior instead of the ``MessageBusInterface``::

.. configuration-block::
// src/MessageBus/QueryBus.php
namespace App\MessageBus;

.. code-block:: php
use Symfony\Component\Messenger\Envelope;
use Symfony\Component\Messenger\HandleTrait;
use Symfony\Component\Messenger\MessageBusInterface;

// src/MessageBus/QueryBus.php
namespace App\MessageBus;
class QueryBus
{
use HandleTrait;

use Symfony\Component\Messenger\Envelope;
use Symfony\Component\Messenger\HandleTrait;
use Symfony\Component\Messenger\MessageBusInterface;
public function __construct(MessageBusInterface $messageBus)
{
$this->messageBus = $messageBus;
}

class QueryBus
/**
* @param object|Envelope $query
*
* @return mixed The handler returned value
*/
public function query($query)
{
use HandleTrait;

public function __construct(MessageBusInterface $messageBus)
{
$this->messageBus = $messageBus;
}

/**
* @param object|Envelope $query
*
* @return mixed The handler returned value
*/
public function query($query)
{
return $this->handle($query);
}
return $this->handle($query);
}
}

.. _`article about CQRS`: https://martinfowler.com/bliki/CQRS.html