EntityListenerPostUpdateTrait

AuthorChangedEvent.php

<?php

namespace App\Command;

class AuthorChangedEvent
{
    private int $bookId;

    public function __construct(Book $book, private array $changedFields, private \DateTime $createdAt)
    {
        $this->bookId = $book->getId();
    }
    
    public function getBookId(): int
    {
        return $this->bookId;
    }
    
    public function getCreatedAt(): \DateTime
    {
        return $this->createdAt;
    }

    public function getChangedFields(): array
    {
        return $this->changedFields;
    }

}

BookListener.php

<?php

namespace App\Doctrine\EventListener;

use App\Command\AuthorChangedEvent;
use App\Entity\Book;
use App\Doctrine\EventListener\Trait\EntityListenerPostUpdateTrait;
use Doctrine\ORM\Event\PreUpdateEventArgs;
use Symfony\Component\Messenger\MessageBusInterface;

class BookListener
{
    use EntityListenerPostUpdateTrait;

    public function __construct(
        private readonly MessageBusInterface $commandBus,
        MessageBusInterface $eventBus,
    ) {
        $this->initEntityListenerPostUpdateTrait($eventBus);
    }

    public function preUpdate(Book $book, PreUpdateEventArgs $eventArgs): void
    {
        if ($eventArgs->hasChangedField('author')) {
            $this->changedFields[] = 'author';
        }
        if (count($this->changedFields) > 0) {
            $this->addEvent(new AuthorChangedEvent($book, $this->changedFields, new \DateTime()));
        }

    }
}

EntityListenerPostUpdateTrait.php

<?php

namespace App\Doctrine\EventListener\Trait;

use Doctrine\Common\Collections\ArrayCollection;
use Doctrine\ORM\Event\PreUpdateEventArgs;
use Symfony\Component\Messenger\MessageBusInterface;

trait EntityListenerPostUpdateTrait
{
    private MessageBusInterface $eventBus;
    private ArrayCollection $events;
    private array $changedFields;

    private function initEntityListenerPostUpdateTrait(MessageBusInterface $eventBus)
    {
        $this->eventBus = $eventBus;
        $this->events = new ArrayCollection();
        $this->changedFields = [];
    }

    /**
     * Add events to the events collection.
     */
    protected function addEvent(): void
    {
        $this->events->add(...func_get_args());
    }

    public function postUpdate(): void
    {
        foreach ($this->events as $event) {
            $this->eventBus->dispatch($event);
        }
        // Reset events after dispatching, otherwise if an entity gets pesisted again before the end of the request,
        // the events will be dispatched again.
        $this->events = new ArrayCollection();
    }

    private function addChangedField(string $changedField, PreUpdateEventArgs $eventArgs): void
    {
        $this->changedFields[] = [
            $changedField => [
                'old' => $eventArgs->getOldValue($changedField),
                'new' => $eventArgs->getNewValue($changedField),
            ],
        ];
    }
}

services.yaml

services:
    # default configuration for services in *this* file
    _defaults:
        autowire: true      # Automatically injects dependencies in your services.
        autoconfigure: true # Automatically registers your services as commands, event subscribers, etc.

   App\Doctrine\EventListener\BookListener:
        tags:
            - { name: doctrine.orm.entity_listener, events: ['preUpdate', 'postUpdate'] }