FooListener Example

Foo.php

<?php

namespace AppBundle\EventListener;

use AppBundle\Entity\FooHistory;
use Doctrine\ORM\Event\PreUpdateEventArgs;

class FooListener
{
    protected $entityManager;

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

    public function preUpdate(Foo $foo, PreUpdateEventArgs $event): void
    {
        // Some custom repository method to get a fooHistory for today
        $fooHistory = $this->entityManager->getRepository(FooHistory::class)
                                                ->findOneForToday($foo->getId());

        // If it doesnt exist - create
        if (!$fooHistory) {
            $fooHistory = new FooHistory();
            $fooHistory->setFooId($foo->getId());
            $fooHistory->setDate(new \DateTime());
        }

        // gethanges() just returns the json_encoded data into a php-assoc array
        $existingHistory = $fooHistory->getChanges() ? $fooHistory->getChangesDecoded() : [];

        // Loop over the change set for this listing
        foreach ($event->getEntityChangeSet() as $field => $changes) {

            $fromValue = ($existingHistory[$field]['fromValue'] ?? $event->getOldValue($field));

            $toValue = $event->getNewValue($field);

            $update = [
                $field => [
                    'fromValue' => $fromValue,
                    'toValue' => $toValue
                ]
            ];

            // Merge the history with the existing history - if it exists
            $existingHistory = array_merge($existingHistory, $update);

            $fooHistory->setChanges(json_encode($existingHistory));
        }

        // Only queue up to be saved if it has a change history
        $this->fooHistory = $fooHistory->getChanges() ? $fooHistory : null;
    }

    /**
     * Write the fooHistory to the DB
     */
    public function postUpdate()
    {
        // If we have something to persist, do it
        if ($this->fooHistory) {
            $this->entityManager->persist($this->fooHistory);
            $this->entityManager->flush();
        }

        $this->fooHistory = null;
    }
}