When to use Entity Manager in Symfony2

Looking at Controller getDoctrine() equals to $this->get('doctrine'), an instance of Symfony\Bundle\DoctrineBundle\Registry. Registry provides:

• getEntityManager() returning Doctrine\ORM\EntityManager, which in turn provides getRepository()
• getRepository() returning Doctrine\ORM\EntityRepository

Thus, $this->getDoctrine()->getRepository() equals $this->getDoctrine()->getEntityManager()->getRepository().

Entity manager is useful when you want to persist or remove an entity:

$em = $this->getDoctrine()->getEntityManager();$em->persist($myEntity);$em->flush();

If you are just fetching data, you can get only the repository:

$repository = $this->getDoctrine()->getRepository('AcmeStoreBundle:Product');$product    = $repository->find(1);

Or better, if you are using custom repositories, wrap getRepository() in a controller function as you can get auto-completition feature from your IDE:

/** * @return \Acme\HelloBundle\Repository\ProductRepository */protected function getProductRepository(){    return $this->getDoctrine()->getRepository('AcmeHelloBundle:Product');}

I think that the getDoctrine()->getRepository() is simply a shortcut to getDoctrine()->getEntityManager()->getRepository(). Did not check the source code, but sounds rather reasonable to me.

If you plan to do multiple operations with the entity manager (like get a repository, persist an entity, flush, etc), then get the entity manager first and store it in a variable. Otherwise, you can get the repository from the entity manager and call whatever method you want on the repository class all in one line. Both ways will work. It's just a matter of coding style and your needs.