Doctrine2 listener for use in SF2 to apply inheritance discriminator map based on DI parameters

Config.yml

# params - base
 
discriminator_map_bundle_ids:
    mychildbundle1: 2
    mychildbundle2: 3
 
# params in each child bundle
 
discriminator_map.mychildbundle1:
    - { parent: 'My\BaseBundle\Entity\Entity1', child: 'My\ChildBundle1\Entity\Entity1' }
    - { parent: 'My\BaseBundle\Entity\Entity2', child: 'My\ChildBundle1\Entity\Entity2' }
 
# listener service, in base
 
my.base.listener.addinheritancemappings:
    class: My\BaseBundle\Doctrine\Listener\AddInheritanceMappings
    arguments: [ %discriminator_map_bundle_ids%, @service_container ]
    tags:
        - { name: doctrine.event_listener, event: loadClassMetadata }
 
# Mapping in parent bundle
 
My\BaseBundle\Entity\Entity1:
  type: entity
  inheritanceType: SINGLE_TABLE
  discriminatorColumn:
    name: entity_type
    type: integer
    length: 11
  discriminatorMap:
    0: MyEntity
 
# Child mapping
 
My\ChildBundle\Entity\Entity1:
  type: entity

Listener.php

<?php
/**
* (c) Ben Lumley <ben@benlumley.co.uk>
*/
 
namespace My\BaseBundle\Doctrine\Listener;
 
use Doctrine\ORM\Event\LoadClassMetadataEventArgs;
 
class AddInheritanceMappings
{
    protected $bundle_ids;
    protected $discriminator_map;
 
    public function __construct($bundle_ids, $container)
    {
        $this->bundle_ids = $bundle_ids;
        foreach ($bundle_ids as $bundle => $id) {
            if ($container->hasParameter('discriminator_map.' . $bundle)) {
                $this->discriminator_map[$bundle] = $container->getParameter('discriminator_map.' . $bundle);
            }
        }
    }
 
    public function loadClassMetadata(LoadClassMetadataEventArgs $eventArgs)
    {
        if (empty($this->discriminator_map)) {
            return;
        }
 
        $metadata = $eventArgs->getClassMetaData();
        $class = $metadata->getName();
 
        foreach ($this->discriminator_map as $bundle=>$mappings) {
            foreach ($mappings as $map) {
                if ($class == $map['parent']) {
                    $metadata->addDiscriminatorMapClass($this->bundle_ids[$bundle], $map['child']);
                }
            }
        }
    }
}