Doctrine MongoDB Event Subscriber to Remove DBRefs of Deleted Documents

ReferencedDocumentInterface.php

<?php


/**
 * Interface ReferencedDocumentInterface
 *
 */
interface ReferencedDocumentInterface
{

    /**
     * @return mixed
     */
    public function getId();

    /**
     * Returns an array with the entity name as key and the field property as value.
     *
     * @return array
     */
    public function getReferingValueFields();

    /**
     * Returns an array with the entity name as key and the field property as value.
     *
     * @return array
     */
    public function getReferingCollectionFields();

}

RemoveReferencesListener.php

<?php

use Doctrine\Common\EventSubscriber;
use Doctrine\ODM\MongoDB\DocumentManager;
use Doctrine\ODM\MongoDB\Event\LifecycleEventArgs;
use Doctrine\ODM\MongoDB\Events;

/**
 * Class RemoveReferencesListener
 *
 */
class RemoveReferencesListener
    implements EventSubscriber
{

    /**
     * @param LifecycleEventArgs $args
     */
    public function preRemove(LifecycleEventArgs $args)
    {
        $document = $args->getDocument();
        $documentManager = $args->getDocumentManager();
        if (!($document instanceof ReferencedDocumentInterface)) {
            return;
        }

        foreach ($document->getReferingValueFields() as $targetDocument => $field) {
            $fields = is_array($field) ? $field : [$field];
            foreach ($fields as $key) {
                $this->removeSingleValuedReference($documentManager, $document, $targetDocument, $key);
            }
        }

        foreach ($document->getReferingCollectionFields() as $targetDocument => $field) {
            $fields = is_array($field) ? $field : [$field];
            foreach ($fields as $key) {
                $this->removeCollectionValuedReference($documentManager, $document, $targetDocument, $key);
            }
        }
    }

    /**
     * @param DocumentManager $documentManager
     * @param ReferencedDocumentInterface $document
     * @param $targetDocument
     * @param $field
     */
    protected function removeSingleValuedReference($documentManager, $document, $targetDocument, $field)
    {
        $id = $document->getId();
        $searchField = $this->parseSearchField($field);

        $queryBuilder = $documentManager->createQueryBuilder($targetDocument);
        $queryBuilder
            ->update()
            ->multiple(true)
            ->field($field)->set(null)
            ->field($searchField)->equals($id);

        $query = $queryBuilder->getQuery();
        $query->execute();
    }

    /**
     * @param DocumentManager $documentManager
     * @param ReferencedDocumentInterface $document
     * @param $targetDocument
     * @param $field
     */
    protected function removeCollectionValuedReference($documentManager, $document, $targetDocument, $field)
    {
        $id = $document->getId();
        $searchField = $this->parseSearchField($field);
        list($field, $matcher) = explode('.', $searchField, 2);
        $matcher = $matcher ? $matcher : '$id';

        $queryBuilder = $documentManager->createQueryBuilder($targetDocument);
        $queryBuilder
            ->update()
            ->multiple(true)
            ->field($field)->pull([
                $matcher => $id,
            ])
            ->field($searchField)->equals($id);

        $query = $queryBuilder->getQuery();
        $query->execute();
    }

    /**
     * This method makes it possible to remove references in embedded collections.
     * E.g.:
     * Embedded reference field: items.$.asset will set items.$.asset to null
     * Embedded reference collection: items.$.assets will pull the asset out of the selected embedded collection
     *
     * @param $field
     *
     * @return string
     */
    protected function parseSearchField($field)
    {
        return str_replace('.$.', '.', $field) . '.$id';
    }

    /**
     * Returns an array of events this subscriber wants to listen to.
     *
     * @return array
     */
    public function getSubscribedEvents()
    {
        return [Events::preRemove];
    }

}