Doctrine2: association mapping for a table with multiple foreign keys - php

Question

A friend of mine and me are working on a multilingual web-application for storing recipes. We use Doctrine 2.1.1 for persistence. At the moment I stuck generating models for an entity and hope someone can give me a hint, or show up a best practice for our case.
I'll try to explain our ERD broadly. Feel free to ask, if there is something unintelligible. Our application has the Entities recipe, ingredients, units (measure units for ingredients) and categories. Each of these entities is stored in an own table. Each entity can be translated in multiple languages. Storage of the translations is intended in a table called (you name it) translations.
Now it will be a bit tricky… we have an extra table called mnemonic. We use it for identifying recipes, ingredients, categories and units of measure in a global context… best analogy to this is a GUID I think. The mnemonic also helps us to map between recipes, ingredients etc. and their translations.
The mnemonic table consists of five rows: id (the primary key) and four additional meta-data rows: ingredient_id, recipe_id, category_id and unit_id referencing a 1:1 relationships to primary key of their relatives.
I'm asking myself how cam I map the relationship between the mnemonic entity and recipes, ingredients an so on.
Or (to be more specific) how can the category_id in the mnemonic table be automatically populated with the value of the the primary key of the category table?
I tried first this kind of association mapping in my Category model:
class Category
{
/**
* #var integer $id
*
* #Column(name="id", type="bigint", nullable=false)
* #Id
* #GeneratedValue(strategy="IDENTITY")
* #OneToOne(targetEntity="Mnemonic", mappedBy="category")
* #JoinColumn(name="id", referencedColumnName="category_id")
*/
private $id;
and in the Mnemonic model:
class Mnemonic
{
/**
*
* #OneToOne(targetEntity="Category", inversedBy="mnemonic")
* #JoinColumn(name="category_id", referencedColumnName="id")
*/
private $categoryId;
That didn't work out — Doctrine dont' produce any errors, but populates only the category table.
So I thought I could write some code in the __construct method of the Category model, where I would create a Mnemonic object, set his categoryId according to the ID of Category model and bind it to doctrine's entity manager. But that's kind of ugly — I think model classes should not be responsible for persistence.
During the writing of my question I thought, that the solution could be a kind of a Factory class. It would take all the persistence logic out of the model and could handle special cases.
What do you think? What is the best solution?
Best regards in advice
Paul

Answer 1

Have you thought about adding an event listener for onFlush? so essentially on flush, you check what object you are persisting, then execute some code such as creating the Mnemonic object.
Info about registering onFlush events can be found on the doctrine website at the following link:
http://docs.doctrine-project.org/projects/doctrine-orm/en/2.0.x/reference/events.html#onflush