James Murty
37f92b3a3f
This change fixes an issue where django-polymorphic raises a `ParentAdminNotRegistered` exception when you register an admin for a child model ancestor, but not for the root ancestor as pointed to by the `polymorphic_ctype` field. This error occurs only when you *Save* the child model detail form, not when you *Save and continue* on that same form. This situation occurs for us when using django-fluent-pages version 1.0.1 which has an intermediate `Page` model registered with a parent admin to show the pages listing. The existing `_get_parent_admin` method expects an admin to be registered for the root `UrlNode` model pointed to by the `polymorphic_ctype` field. This fix uses a potentially naive and slow brute-force approach where it walks up the class hierarchy and checks whether a parent admin is registered for each ancestor model, unless/until it finds one. See also https://github.com/ic-labs/django-icekit/issues/31/
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Polymorphic Models for Django
=============================
Django-polymorphic simplifies using inherited models in Django projects.
When a query is made at the base model, the inherited model classes are returned.
When we store models that inherit from a ``Project`` model...
.. code-block:: python
>>> Project.objects.create(topic="Department Party")
>>> ArtProject.objects.create(topic="Painting with Tim", artist="T. Turner")
>>> ResearchProject.objects.create(topic="Swallow Aerodynamics", supervisor="Dr. Winter")
...and want to retrieve all our projects, the subclassed models are returned!
.. code-block:: python
>>> Project.objects.all()
[ <Project: id 1, topic "Department Party">,
<ArtProject: id 2, topic "Painting with Tim", artist "T. Turner">,
<ResearchProject: id 3, topic "Swallow Aerodynamics", supervisor "Dr. Winter"> ]
Using vanilla Django, we get the base class objects, which is rarely what we wanted:
.. code-block:: python
>>> Project.objects.all()
[ <Project: id 1, topic "Department Party">,
<Project: id 2, topic "Painting with Tim">,
<Project: id 3, topic "Swallow Aerodynamics"> ]
This also works when the polymorphic model is accessed via
ForeignKeys, ManyToManyFields or OneToOneFields.
Features
--------
* Full admin integration.
* ORM integration:
* support for ForeignKey, ManyToManyField, OneToOneField descriptors.
* Filtering/ordering of inherited models (``ArtProject___artist``).
* Filtering model types: ``instance_of(...)`` and ``not_instance_of(...)``
* Combining querysets of different models (``qs3 = qs1 | qs2``)
* Support for custom user-defined managers.
* Uses the minumum amount of queries needed to fetch the inherited models.
* Disabling polymorphic behavior when needed.
While *django-polymorphic* makes subclassed models easy to use in Django,
we still encourage to use them with caution. Each subclassed model will require
Django to perform an ``INNER JOIN`` to fetch the model fields from the database.
While taking this in mind, there are valid reasons for using subclassed models.
That's what this library is designed for!
For more information, see the `documentation at Read the Docs <https://django-polymorphic.readthedocs.io/>`_.
Installation
------------
Install using ``pip``\ ...
.. code:: bash
$ pip install django-polymorphic
License
=======
Django-polymorphic uses the same license as Django (BSD-like).