This chapter explains how references between documents are mapped with Doctrine.
Examples of many-valued references in this manual make use of a Collection
interface and a corresponding ArrayCollection implementation, which are
defined in the Doctrine\Common\Collections namespace. These classes have no
dependencies on ODM, and can therefore be used within your domain model and
elsewhere without introducing coupling to the persistence layer.
ODM also provides a PersistentCollection implementation of Collection,
which incorporates change-tracking functionality; however, this class is
constructed internally during hydration. As a developer, you should develop with
the Collection interface in mind so that your code can operate with any
implementation.
Note
New in 1.1: you are no longer limited to using ArrayCollection and can
freely use your own Collection implementation. For more details please
see :doc:`Custom Collections <custom-collections>` chapter.
Why are these classes used over PHP arrays? Native arrays cannot be
transparently extended in PHP, which is necessary for many advanced features
provided by the ODM. Although PHP does provide various interfaces that allow
objects to operate like arrays (e.g. Traversable, Countable,
ArrayAccess), and even a concrete implementation in ArrayObject, these
objects cannot always be used everywhere that a native array is accepted.
Doctrine's Collection interface and ArrayCollection implementation are
conceptually very similar to ArrayObject, with some slight differences and
improvements.
Reference one document:
.. configuration-block::
.. code-block:: php
<?php
/** @Document */
class Product
{
// ...
/**
* @ReferenceOne(targetDocument=Shipping::class)
*/
private $shipping;
// ...
}
/** @Document */
class Shipping
{
// ...
}
.. code-block:: xml
<?xml version="1.0" encoding="UTF-8"?>
<doctrine-mongo-mapping xmlns="http://doctrine-project.org/schemas/odm/doctrine-mongo-mapping"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://doctrine-project.org/schemas/odm/doctrine-mongo-mapping
http://doctrine-project.org/schemas/odm/doctrine-mongo-mapping.xsd">
<document name="Documents\Product">
<reference-one field="shipping" target-document="Documents\Shipping" />
</document>
</doctrine-mongo-mapping>
Reference many documents:
.. configuration-block::
.. code-block:: php
<?php
/** @Document */
class User
{
// ...
/**
* @ReferenceMany(targetDocument=Account::class)
*/
private $accounts = [];
// ...
}
/** @Document */
class Account
{
// ...
}
.. code-block:: xml
<?xml version="1.0" encoding="UTF-8"?>
<doctrine-mongo-mapping xmlns="http://doctrine-project.org/schemas/odm/doctrine-mongo-mapping"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://doctrine-project.org/schemas/odm/doctrine-mongo-mapping
http://doctrine-project.org/schemas/odm/doctrine-mongo-mapping.xsd">
<document name="Documents\Product">
<reference-many field="accounts" target-document="Documents\Account" />
</document>
</doctrine-mongo-mapping>
If you want to store different types of documents in references, you can simply
omit the targetDocument option:
.. configuration-block::
.. code-block:: php
<?php
/** @Document */
class User
{
// ..
/** @ReferenceMany */
private $favorites = [];
// ...
}
.. code-block:: xml
<field field-name="favorites" />
Now the $favorites property can store a reference to any type of document!
The class name will be automatically stored in a field named
_doctrine_class_name within the DBRef object.
Note
The MongoDB shell tends to ignore fields other than $id and $ref
when displaying DBRef objects. You can verify the presence of any $db
and discriminator fields by querying and examining the document with a
driver. See SERVER-10777
for additional discussion on this issue.
The name of the field within the DBRef object can be customized via the
discriminatorField option:
.. configuration-block::
.. code-block:: php
<?php
/** @Document */
class User
{
// ..
/**
* @ReferenceMany(discriminatorField="type")
*/
private $favorites = [];
// ...
}
.. code-block:: xml
<reference-many field-name="favorites">
<discriminator-field name="type" />
</reference-many>
You can also specify a discriminator map to avoid storing the |FQCN| in each DBRef object:
.. configuration-block::
.. code-block:: php
<?php
/** @Document */
class User
{
// ..
/**
* @ReferenceMany(
* discriminatorMap={
* "album"=Album::class,
* "song"=Song::class
* }
* )
*/
private $favorites = [];
// ...
}
.. code-block:: xml
<reference-many field-name="favorites">
<discriminator-map>
<discriminator-mapping value="album" class="Documents\Album" />
<discriminator-mapping value="song" class="Documents\Song" />
</discriminator-map>
</reference-many>
If you have references without a discriminator value that should be considered a certain class, you can optionally specify a default discriminator value:
.. configuration-block::
.. code-block:: php
<?php
/** @Document */
class User
{
// ..
/**
* @ReferenceMany(
* discriminatorMap={
* "album"=Album::class,
* "song"=Song::class
* },
* defaultDiscriminatorValue="album"
* )
*/
private $favorites = [];
// ...
}
.. code-block:: xml
<reference-many field-name="favorites">
<discriminator-map>
<discriminator-mapping value="album" class="Documents\Album" />
<discriminator-mapping value="song" class="Documents\Song" />
</discriminator-map>
<default-discriminator-value value="album" />
</reference-many>
By default all references are stored as a DBRef object with the traditional
$ref, $id, and (optionally) $db fields (in that order). For references to
documents of a single collection, storing the collection (and database) names for
each reference may be redundant. You can use ID references to store the
referenced document's identifier (e.g. MongoDB\BSON\ObjectId) instead of a
DBRef.
Example:
.. configuration-block::
.. code-block:: php
<?php
/**
* @ReferenceOne(targetDocument=Profile::class, storeAs="id")
*/
private $profile;
.. code-block:: xml
<reference-one target-document="Documents\Profile", store-as="id" />
Now, the profile field will only store the MongoDB\BSON\ObjectId of the
referenced Profile document.
ID references reduce the amount of storage used, both for the document itself and any indexes on the reference field; however, ID references cannot be used with discriminators, since there is no DBRef object in which to store a discriminator value.
In addition to saving references as DBRef with $ref, $id, and $db
fields and as MongoDB\BSON\ObjectId, it is possible to save references as
DBRef without the $db field. This solves problems when the database name
changes (and also reduces the amount of storage used).
The storeAs option has the following possible values:
- dbRefWithDb: Uses a DBRef with
$ref,$id, and$dbfields - dbRef: Uses a DBRef with
$refand$id(this is the default) - ref: Uses a custom embedded object with an
idfield - id: Uses the identifier of the referenced object
Note
Up until 2.0 storeAs=dbRefWithDb was the default setting. If you have data in
the old format, you should add storeAs=dbRefWithDb to all your references, or
update the database references (deleting the $db field) as storeAs=dbRef
is the new default setting.
By default, Doctrine will not cascade any UnitOfWork operations to
referenced documents. You must explicitly enable this functionality:
.. configuration-block::
.. code-block:: php
<?php
/**
* @ReferenceOne(targetDocument=Profile::class, cascade={"persist"})
*/
private $profile;
.. code-block:: xml
<reference-one target-document="Documents\Profile">
<cascade>
<persist/>
</cascade>
</reference-one>
The valid values are:
- all - cascade all operations by default.
- detach - cascade detach operation to referenced documents.
- merge - cascade merge operation to referenced documents.
- refresh - cascade refresh operation to referenced documents.
- remove - cascade remove operation to referenced documents.
- persist - cascade persist operation to referenced documents.
There is another concept of cascading that is relevant only when removing documents
from collections. If a Document of type A contains references to privately
owned Documents B then if the reference from A to B is removed the
document B should also be removed, because it is not used anymore.
OrphanRemoval works with both reference one and many mapped fields.
Note
When using the orphanRemoval=true option Doctrine makes the assumption
that the documents are privately owned and will NOT be reused by other documents.
If you neglect this assumption your documents will get deleted by Doctrine even if
you assigned the orphaned documents to another one.
As a better example consider an Addressbook application where you have Contacts, Addresses and StandingData:
<?php
namespace Addressbook;
use Doctrine\Common\Collections\ArrayCollection;
/**
* @Document
*/
class Contact
{
/** @Id */
private $id;
/** @ReferenceOne(targetDocument=StandingData::class, orphanRemoval=true) */
private $standingData;
/** @ReferenceMany(targetDocument=Address::class, mappedBy="contact", orphanRemoval=true) */
private $addresses;
public function __construct()
{
$this->addresses = new ArrayCollection();
}
public function newStandingData(StandingData $sd): void
{
$this->standingData = $sd;
}
public function removeAddress($pos): void
{
unset($this->addresses[$pos]);
}
}Now two examples of what happens when you remove the references:
<?php
$contact = $dm->find(Addressbook\Contact::class, $contactId);
$contact->newStandingData(new StandingData("Firstname", "Lastname", "Street"));
$contact->removeAddress(1);
$dm->flush();In this case you have not only changed the Contact document itself but
you have also removed the references for standing data and as well as one
address reference. When flush is called not only are the references removed
but both the old standing data and the one address documents are also deleted
from the database.