sort objects with several parameters - symfony2 - symfony

Question

I want to display a list of objects ordered by a parameter that depends of several fields of the entity.
I have created an entity, let's call it Object for instance, which has an id and 2 integers as fields. I work with Symfony 2 and Doctrine as ORM.
`/**
* Object
*
* #ORM\Table(name="object")
* #ORM\Entity(repositoryClass="AppBundle\Repository\ObjectRepository")
*/
class Object
{
/**
* #var int
*
* #ORM\Column(name="id", type="integer")
* #ORM\Id
* #ORM\GeneratedValue(strategy="AUTO")
*/
private $id;
/**
* #var int
*
* #ORM\Column(name="field1", type="int")
*/
private $field1;
/**
* #var int
*
* #ORM\Column(name="field2", type="int")
*/
private $field2;
}
Now I would like to get the top-5 instances of Object from my database ordered by, for example, the average between field1 and field2, to display them in a twig template.
I know I can use this:
$list = $this->getDoctrine()->getRepository('AppBundle:Object')->findAll();
to get a list of all existing instances of Object in the DB, but although it might be a relatively simple question to experimented Symfony programmers, I have no idea about how to order it by avg(field1,field2).

Answer 1

You could create a method in your repository that builds a query containing a special ORDER BY clause and that limits the number of results to 5. It could look like this:
class ObjectRepository extends \Doctrine\ORM\EntityRepository
{
/* ... other methods ... */
public function retrieveTopObjects($limit = 5)
{
$qb = $this->createQueryBuilder('o')->orderBy('(o.field1 + o.field2) / 2', 'DESC');
$qb->setMaxResults($limit);
return $qb->getQuery()->getResult();
}
}
If you would like to have the score used to sort entities along with your objects, you would need to add $qb->addSelect('(o.field1 + o.field2) / 2 AS score') and then use $qb->orderBy('score', 'DESC') instead of the expression shown above.
In such a case, you would end up with a mixed result as explained in the documentation.