Document class inheritance¶
Mapped documents can simply extend each other. Mappings of the base class are inherited for the extending class. It is even possible to overwrite the mapping of the base class, but you should be very careful with that, as this can lead to semantically broken data structures.
Overwriting mixins works as overwriting any other setting. This means that if your mapping has any mixins, you need to explicitly repeat any mixins from anchestor classes that you want to keep.
Typically, the purpose of such inheritance is to model the is-a relationship in your models and to reuse the mappings and functions of the base class.
Contrary to ORM, the PHPCR-ODM with its NoSQL nature can handle documents that extend each other just like any other document. This means both your super class and the extending classes can be concrete classes and be stored in the repository. If you explicitly want to declare that objects of a class should not be persisted, you can use MappedSuperclass to provide common mappings but prevent such objects from being stored.
There are also no restrictions on referencing between any of those classes.
You can also query for them, but if you query for documents of a specific type, you will not find the super type documents.
To use this feature, just have your document classes extend each other. You should not repeat mappings that exist in the super class, they are inherited automatically.
Doctrine will follow the inheritance of your document class. As soon as one class is not mapped, it will stop the process. Make sure to map all parent classes if you have a deep inheritance tree.