You are browsing a version that is no longer maintained.
Maintained
2.10.2 (upcoming) 2.9.2 (current)
Unmaintained
2.11 2.8 2.7 2.6 2.5 2.4 2.3 2.2 2.1 2.0 1.3 1.2 1.1 1.0

Inheritance Mapping

Doctrine currently offers two supported methods of inheritance: single collection and collection per class inheritance.

Mapped Superclasses

A mapped superclass is an abstract or concrete class that provides mapping information for its subclasses, but is not itself a document. Typically, the purpose of such a mapped superclass is to define state and mapping information that is common to multiple document classes.

Just like non-mapped classes, mapped superclasses may appear in the middle of an otherwise mapped inheritance hierarchy (through single collection or collection per class) inheritance.

A mapped superclass cannot be a document and is not queryable.

Example:

<?phpnamespace Documents;/** @MappedSuperclass */abstract class BaseDocument{}

Single Collection Inheritance

In single collection inheritance, each document is stored in a single collection and a discriminator field is used to distinguish one document type from another.

Simple example:

<?phpnamespace Documents;/** * @Document * @InheritanceType("SINGLE_COLLECTION") * @DiscriminatorField("type") * @DiscriminatorMap({"person"=Person::class, "employee"=Employee::class}) */class Person{    // ...}/** * @Document */class Employee extends Person{    // ...}

The discriminator value allows Doctrine to infer the class name to instantiate when hydrating a document. If a discriminator map is used, the discriminator value will be used to look up the class name in the map.

Now, if we query for a Person and its discriminator value is employee, we would get an Employee instance back:

<?php$employee = new Employee();// ...$dm->persist($employee);$dm->flush();$employee = $dm->find(Person::class, $employee->getId()); // instanceof Employee

Even though we queried for a Person, Doctrine will know to return an Employee instance because of the discriminator map!

If your document structure has changed and you've added discriminators after already having a bunch of documents, you can specify a default value for the discriminator field:

<?phpnamespace Documents;/** * @Document * @InheritanceType("SINGLE_COLLECTION") * @DiscriminatorField("type") * @DiscriminatorMap({"person"=Person::class, "employee"=Employee::class}) * @DefaultDiscriminatorValue("person") */class Person{    // ...}/** * @Document */class Employee extends Person{    // ...}

Collection Per Class Inheritance

With collection per class inheritance, each document is stored in its own collection and contains all inherited fields:

<?phpnamespace Documents;/** * @Document * @InheritanceType("COLLECTION_PER_CLASS") */class Person{    // ...}/** * @Document */class Employee extends Person{    // ...}

A discriminator is not needed with this type of inheritance since the data is separated in different collections.