Get relation of ManyToMany entities - php

Question

I stuck with getting ManyToMany relation. I have two entities Offer and OfferType.
I defined ManyToMany relation only on OfferEntity and it looks like saving offers with multiple OfferType works fine in database I see correct joining table.
OfferEntity.php
/**
* Offer Entity
*
* #ORM\Table(name="offer")
* #ORM\Entity(repositoryClass="ProjectBundle\Repository\OfferRepository")
*/
class Offer
{
/**
* #Assert\Count(
* min = "1",
* minMessage = "You must specify at least one offer type."
* )
* #ORM\ManyToMany(targetEntity="OfferType")
*/
private $types;
public function __construct()
{
$this->types = new ArrayCollection();
}
/**
* #return ArrayCollection
*/
public function getTypes()
{
return $this->types;
}
(...)
Right now, I would like to get all types assigned to the offer. I tried it like this:
// $offer is an Entity
$query = $em->createQueryBuilder()
->select('offer.types')
->from('ProjectBundle:Offer', 'offer')
->where('offer = :offer')
->setParameters([
'offer' => $offer
]);
Unfortunately I getting error:
[2/2] QueryException: [Semantical Error] line 0, col 13 near 'types FROM ProjectBundle:Offer': Error: Invalid PathExpression. Must be a **StateFieldPathExpression**.
[1/2] QueryException: SELECT offer.types FROM ProjectBundle:Offer offer WHERE offer = :offer
Based on StackOverflow answers for similar questions tried it also to use IDENTITY():
// $offer is an Entity
$query = $em->createQueryBuilder()
->select('IDENTITY(offer.types)')
->from('ProjectBundle:Offer', 'offer')
->where('offer = :offer')
->setParameters([
'offer' => $offer
]);
But then I have:
[2/2] QueryException: [Semantical Error] line 0, col 22 near 'types) FROM ProjectBundle:Offer': Error: Invalid PathExpression. Must be a SingleValuedAssociationField.
[1/2] QueryException: SELECT IDENTITY(offer.types) FROM ProjectBundle:Offer offer WHERE offer = :offer
I would really appreciate any hints about getting ManyToMany relation, maybe my approach for this is incorrect?

Answer 1

Your approach is not quite right. You need to join the entity you want to load. You should spend a bit more time reading the doctrine documentation on entity relations & querybuilder.
Like so.
$query = $em->createQueryBuilder()
->select('offer', 'types')
->from('ProjectBundle:Offer', 'offer')
->join('offer.types', 'types')
->where('offer = :offer')
->setParameters([
'offer' => $offer
]);
Then your result will contain what you want.
Note: you don't even have to join types to get types from an offer, you could also use
$offer->getTypes()
And types will lazy load in standard doctrine manner.
But querying it as above will load types in advance - so you avoid lazy loading. This may or may not be a better approach depending on requirements.

Answer 2

If you have your many to many mappings set up only on one side, you'll only be able to query for the Offer and then retrieve the types from it:
$builder = $em->createQueryBuilder()
->select('o', 't')
->from('ProjectBundle:Offer', 'o')
->join('o.types', 't')
->where('o.id = :offer')
->setParameter('offer', $offerId);
$offer = $builder->getQuery()->getOneOrNullResult();
$types = $offer->getTypes();
That was assuming you only had $offerId to work with. If you already have the whole Offer instance, you might just as well just call getTypes() on it and doctrine will take care of the rest.
If you were to define the inverse mappings on the OfferType entity like so:
class OfferType
{
/**
* #ORM\ManyToMany(targetEntity="Offer", mappedBy="types")
*/
private $offers;
}
You could make queries for just the types:
$builder = $em->createQueryBuilder()
->select('t')
->from('ProjectBundle:OfferType', 't')
->join('t.offers', 'o')
->where('o = :offer')
->setParameter('offer', $offer);
$types = $builder->getQuery()->getResult();