Styjun

Let's say I want to implement the following entities in Doctrine:

Thing represents anything that can perform an action over another Thing. A Relation can contain two entities and a description of the action, and its tuple is unique.

Here are some examples of what I'm trying to achieve:

• Hens (thing) lay (action) eggs (thing)


• Water (thing) extinguishes (action) fire (thing)


• Bob (thing) likes (action) apples (thing)


• Bob (thing) drinks (action) water (thing)

As you can see, order matters (it's not the same "Bob likes apples" as "Apples like Bob").

Despite my best efforts, I can't find any proper way to implement this.

I've tried creating a field called $relations in Thing tagged as "One-To-Many" and then marking $left and $right in Relation as "Many-To-One". The problem is I can't have two inversed sides for the same owning side (at least AFAIK).

This current implementation neither allows for getting all relations for a particular Thing in the $relations field as I'm only able to specify one inversed side.

Here's what I've come up with so far:

/** @ORMEntity */
class Thing 
 /**
 * @ORMId
 * @ORMColumn(type="integer", options="unsigned":true)
 * @ORMGeneratedValue
 */
 protected $id;

 /** @ORMColumn(type="string") */
 protected $name;

 /**
 * @ORMOneToMany(targetEntity="Relation", mappedBy="right")
 */
 protected $relations;



/** @ORMEntity */
class Relation 
 /** @ORMId @ORMColumn(type="string") */
 protected $action;

 /** @ORMId @ORMManyToOne(targetEntity="Thing") */
 private $left;

 /** @ORMId @ORMManyToOne(targetEntity="Thing", inversedBy="relations") */
 private $right;

Turns out Doctrine doesn't directly allow for this kind of relation.

The best solution I could came up with was to create two collections in Thing for the relations instead of one and then defining a method that outputs both:

/** @ORMEntity */
class Thing 
 // [...]

 /** @ORMOneToMany(targetEntity="Relation", mappedBy="left") */
 protected $relationsLeft;

 /** @ORMOneToMany(targetEntity="Relation", mappedBy="right") */
 protected $relationsRight;

 public function getRelations() 
 return new ArrayCollection(array_merge(
 $this->relationsLeft->toArray(),
 $this->relationsRight->toArray()
 ));
 



/** @ORMEntity */
class Relation 
 // [...]

 /** @ORMId @ORMManyToOne(targetEntity="Thing", inversedBy="relationsLeft") */
 private $left;

 /** @ORMId @ORMManyToOne(targetEntity="Thing", inversedBy="relationsRight") */
 private $right;