Get subclass from repository using Class Table Inheritance - php

Question

I have one entity, say Person, which contains a list of $pets:
protected $pets;
public function getPets()
{
return $this->pets;
}
Standard Doctrine. Unfortunately, these pets may be of different types, such as cats or dogs, or a mix. So I used Class Table Inheritance:
/**
* #ORM\Entity
* #ORM\Table(name="pets")
* #ORM\InheritanceType("JOINED")
* #ORM\DiscriminatorColumn(name="pettype", type="string")
* #ORM\DiscriminatorMap({"cat_animal" = "CatAnimal", "dog_animal" = "DogAnimal"})
*/
class Pet
{
/**
* #ORM\Column(name="eventid", type="integer")
* #ORM\Id
*/
private $id; // protected did not work either
/**
* Get id
*/
public function getId()
{
return $this->id;
}
}
/**
* #ORM\Entity
* #ORM\Table(name="cat_animal")
*/
class CatAnimal extends Pet
{
/**
* #ORM\Column(type="float")
*/
protected $height;
// etc.
}
// DogAnimal class omitted.
This was relatively straightforward using Doctrine's docs.
If I want to get all cats for an individual person, I have discovered I can do this:
public function getCats($person)
{
return $this->getEntityManager()->getRepository('MyBundle:CatAnimal')
->findByPerson($person);
}
However, how do I access the subclasses using a query builder? If I have the Person repository ($repos here), I want to do something like the following:
$repos->createQueryBuilder('person')
->select('pet.height')
->join('person.pets', 'pet')
->where('person = :person')
->setParameter('person', $person);
Except Pet doesn't have height, so this throws an exception. The DQL generated automagically joins to DogAnimal and CatAnimal, so I should be able to access these properties, but I don't know how. I have tried:
$repos->createQueryBuilder('person')
->select('cat.height')
->from('MyBundle:CatAnimal', 'cat)
->join('person.pets', 'pet')
->where('person = :person')
->setParameter('person', $person);
But this seems to do the cartesian product. I can solve that by adding:
->andWhere('person.id = cat.person')
This seems overly complicated for what I want. I have tried looking for the correct way to do this, but resources are limited.
This builds on a previous question, with a similar structure. The names of the tables were changed for clarity and generalisability.

Answer 1

You need to join correctly to Person, adding a field to the Pet class. In my example I named it owner:
$catRepo->createQueryBuilder('cat')
->select('cat.height')
->from('MyBundle:CatAnimal', 'cat')
->join('cat.owner', 'person')
->where('person = :person')
->setParameter('person', $person);