Symfony Doctrine现有数据库中的Sluggable扩展

I had to add in an existing entity a slug field to slugify the field 'name'. But there is already data in this entity and I can't delete them.

I would like to create a console script which can slugify all my 'name' field.

I don't know how to do it because this is not an insertion but just an update...

class SlugCommand extends ContainerAwareCommand
{
    protected function configure()
    {
        $this
            ->setName('generate:geo:slug')
            ->setDescription('Slug generation for GeoBundle ');
    }

    protected function execute(InputInterface $input, OutputInterface $output)
    {
        $em = $this->getContainer()->get('doctrine')->getManager();
        $regions = $em->getRepository('FMGeoBundle:Region')->findAll();

        if($regions === null){
            throw new Exception('No Region found');
        }

        foreach($regions as $region){
            // ????? Generate the slug here ??
            $em->persist($region);
        }

        $em->flush();
        $output->writeln('Slugs Generated ;) ...');
    }
}

The 'slug' field in my entity:

/**
 * @var string
 *
 * @ORM\Column(name="slug", type="string", length=255)
 * @Gedmo\Slug(fields={"name"})
 */
protected $slug;