Upcasting

There are cases where the already have events in our stream but there is data missing or not in the right format for our new usecase. Normally you would need to create versioned events for this. This can lead to many versions of the same event which could lead to some chaos. To prevent this we offer Upcaster, which can operate on the payload before denormalizing to an event object. There you can change the event name and adjust the payload of the event.

Info

You can find out more about upcasting in the library documentation. This documentation is limited to bundle integration.

Usage

use Patchlevel\EventSourcing\Serializer\Upcast\Upcast;
use Patchlevel\EventSourcing\Serializer\Upcast\Upcaster;

final class ProfileCreatedEmailLowerCastUpcaster implements Upcaster
{
    public function __invoke(Upcast $upcast): Upcast
    {
        // ignore if other event is processed
        if ($upcast->eventName !== 'profile_created') {
            return $upcast;
        }

        $payload = $upcast->payload;
        $payload['email'] = strtolower($payload['email']);

         return new Upcast($upcast->eventName, $payload)
    }
}

If you have the symfony default service setting with autowireand autoconfigure enabled, the upcaster is automatically recognized and registered at the Upcaster interface. Otherwise you have to define the upcaster in the symfony service file:

services:
    App\Upcaster\ProfileCreatedEmailLowerCastUpcaster:
      tags:
        - event_sourcing.upcaster