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Symfony2 – Franz Jordán 2011
Relationships and Proxy Classes
This "lazy loading" is possible because, when necessary, Doctrine returns a "proxy" object in
place of the true object. Look again at the above example:
$product = $this->getDoctrine()
->getRepository('AcmeStoreBundle:Product')
->find($id);
$category = $product->getCategory();
// prints "Proxies\AcmeStoreBundleEntityCategoryProxy"
echo get_class($category);
This proxy object extends the true Category object, and looks and acts exactly like it. The
difference is that, by using a proxy object, Doctrine can delay querying for the
real Category data until you actually need that data (e.g. until you call$category->getName()).
The proxy classes are generated by Doctrine and stored in the cache directory. And though you'll
probably never even notice that your $category object is actually a proxy object, it's important
to keep in mind.
In the next section, when you retrieve the product and category data all at once (via a join),
Doctrine will return the true Category object, since nothing needs to be lazily loaded.
Joining to Related Records
In the above examples, two queries were made - one for the original object (e.g. a Category)
and one for the related object(s) (e.g. the Product objects).
Remember that you can see all of the queries made during a request via the web debug toolbar.
Of course, if you know up front that you'll need to access both objects, you can avoid the second
query by issuing a join in the original query. Add the following method to
the ProductRepositoryclass:
// src/Acme/StoreBundle/Repository/ProductRepository.php
public function findOneByIdJoinedToCategory($id)
{
$query = $this->getEntityManager()
->createQuery('
SELECT p, c FROM AcmeStoreBundle:Product p
JOIN p.category c
WHERE p.id = :id'
)->setParameter('id', $id);
}
try {
return $query->getSingleResult();
} catch (\Doctrine\ORM\NoResultException $e) {
}
return null;
Now, you can use this method in your controller to query for a Product object and its
relatedCategory with just one query:
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