Entity associated with non-entity - symfony

Question

I have an interface SupplierInterface with 2 implementations: B2BSupplier (a Doctrine entity), RetailSupplier (a static object).
<?php
namespace MyBundle\Model;
interface SupplierInterface {
const B2B = 'B2B';
const RETAIL = 'Retail';
/**
* #return string
*/
public function getSupplierType();
/**
* #return string
*/
public function __toString();
}
Another entity, Supply has a many-to-one relationship with a Supplier. Normally this isn't problematic. But because RetailSupplier is not a Doctrine entity, I'm a bit flummoxed about how to proceed.
Supply looks like this:
<?php
namespace MyBundle\Entity;
use Doctrine\ORM\Mapping as ORM;
use Doctrine\Common\Collections\ArrayCollection;
use Symfony\Component\Validator\Constraints as Assert;
use Gedmo\Blameable\Traits\BlameableEntity;
use Gedmo\Timestampable\Traits\TimestampableEntity;
/**
* Supply
*
* #ORM\Table(name="cir_supply")
* #ORM\Entity()
*/
class Supply
{
use BlameableEntity;
use TimestampableEntity;
/**
* #var int
* #ORM\Column(name="id", type="integer")
* #ORM\Id
* #ORM\GeneratedValue(strategy="AUTO")
*/
protected $id;
/**
* #ORM\ManyToOne(targetEntity="B2BSupplier")
* #ORM\JoinColumn(name="supplier_id", referencedColumnName="id", nullable=true)
*/
protected $supplier; // <-- PROBLEM, since supplier could be B2BSupplier entity, or it could be vanilla object RetailSupplier
/**
* #ORM\ManyToOne(targetEntity="Chemical", inversedBy="supplies")
* #ORM\JoinColumn(name="chemical_id", referencedColumnName="id", nullable=false)
*/
protected $chemical;
/**
* #ORM\Column(name="external_id", type="string")
*/
protected $externalId;
//getters and setters ...
}
How do I specify a Doctrine relationship when that relationship might not always be valid?

Answer 1

From my experience I'm 99% sure you can't do what you want in your current setup. That being said, there are a few workarounds I can think of. Also before I go into the workarounds. You should think if you really want OneToOne relation on 'supplier' or will ManyToOne work better. OneToOne has some Lazy loading issues and also Workaround 3 work better with ManyToOne.
Workaround 1:
Remove the relation and make the supplier filed contain the id, without having a relation defined.
Extend SupplierRepository 'find' method to handle the cases where id is
2.1 'null' there is no relation in witch case it returns RetailSupplier
2.2 call parent::find for all other cases
2.3 Optional: if null relations are required change 2.1 to use '0' instead of null (adds con 3)
Pros:
fast to achieve from your current setup
keep database foreign key (if step 2.3 is ignored)
Cons:
hidden behavior of the 'find' method
you loose the your doctrine relation
not scalable for other types of Suppliers
source of the information is split between the app and the database
if step 2.3 is required, you loose database foraign key ('0' will not be a foraign key)
Workaround 2:
Modify getSupplier to return RetailSupplier if $this->supplier is null
Modify setSupplier to set null if $supplier is instance of RetailSupplyer
Optinal: Change the first 2 steps to handle '0' as RetailSupplyer and 'null' as no relation
Pros:
fast to achieve from your current setup
keep database foreign key (if step 3 is ignored)
keep doctrine relation
Cons:
hidden behavior of the setter and getter
not scalable for other types of Suppliers
if step 3 is required, you loose database foraign key ('0' will not be a foraign key)
source of the information is split between the app and the database
Workaround 3 (doctrine inheritance mapping):
Create an abstract (called Supplier) this will be inherited by RetailSupplyer and B2BSupplier
Add inheritance metadata to Supplier abstract something like this
Create an entity for RetailSupplyer and a database table with one single line to start (the first RetailSupplier)
Change your database to match your inheritance mapping settings (for more info http://docs.doctrine-project.org/projects/doctrine-orm/en/latest/reference/inheritance-mapping.html)
Change your relation to ManyToOne on $supplier and make it to point to Supplier
Pros:
source of the information is only the database
no hidden behavior in your code
scalable for other types of suppliers and other more retail suppliers
Cons:
harder to achieve from your current setup (database changes, new doctrine setup, possibly some refactor)
pros/cons: Depending on the selected inheritance type you can have full relation path in your database (with foraign key), or you can have no relations. This is up to you ;) after you read the documentation for inheritance mapping.
PS: If I had to choose i will go with Workaround 3. It is hardest to achieve, but solid do it.
Hope this helps and happy coding
Alexandru Cosoi