django-polymorphic/docs/third-party.rst

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Third-party applications support
================================
django-mptt support
-------------------
Combining polymorphic with django-mptt_ is certainly possible, but not straightforward.
It involves combining both managers, querysets, models, meta-classes and admin classes
using multiple inheritance.
The django-polymorphic-tree_ package provides this out of the box.
django-reversion support
------------------------
Support for django-reversion_ works as expected with polymorphic models.
However, they require more setup than standard models. That's become:
* Manually register the child models with django-reversion_, so their ``follow`` parameter can be set.
* Polymorphic models use `multi-table inheritance <https://docs.djangoproject.com/en/dev/topics/db/models/#multi-table-inheritance>`_.
See the `reversion documentation <https://django-reversion.readthedocs.io/en/latest/api.html#multi-table-inheritance>`_
how to deal with this by adding a ``follow`` field for the primary key.
* Both admin classes redefine ``object_history_template``.
Example
~~~~~~~
The admin :ref:`admin example <admin-example>` becomes:
.. code-block:: python
from django.contrib import admin
from polymorphic.admin import PolymorphicParentModelAdmin, PolymorphicChildModelAdmin
from reversion.admin import VersionAdmin
from reversion import revisions
from .models import ModelA, ModelB, ModelC
class ModelAChildAdmin(PolymorphicChildModelAdmin, VersionAdmin):
base_model = ModelA
base_form = ...
base_fieldsets = (
...
)
class ModelBAdmin(ModelAChildAdmin, VersionAdmin):
# define custom features here
class ModelCAdmin(ModelBAdmin):
# define custom features here
class ModelAParentAdmin(VersionAdmin, PolymorphicParentModelAdmin):
base_model = ModelA
child_models = (
(ModelB, ModelBAdmin),
(ModelC, ModelCAdmin),
)
revisions.register(ModelB, follow=['modela_ptr'])
revisions.register(ModelC, follow=['modelb_ptr'])
admin.site.register(ModelA, ModelAParentAdmin)
Redefine a :file:`admin/polymorphic/object_history.html` template, so it combines both worlds:
.. code-block:: html+django
{% extends 'reversion/object_history.html' %}
{% load polymorphic_admin_tags %}
{% block breadcrumbs %}
{% breadcrumb_scope base_opts %}{{ block.super }}{% endbreadcrumb_scope %}
{% endblock %}
This makes sure both the reversion template is used, and the breadcrumb is corrected for the polymorphic model.
.. _django-reversion-compare-support:
django-reversion-compare support
--------------------------------
The django-reversion-compare_ views work as expected, the admin requires a little tweak.
In your parent admin, include the following method:
.. code-block:: python
def compare_view(self, request, object_id, extra_context=None):
"""Redirect the reversion-compare view to the child admin."""
real_admin = self._get_real_admin(object_id)
return real_admin.compare_view(request, object_id, extra_context=extra_context)
As the compare view resolves the the parent admin, it uses it's base model to find revisions.
This doesn't work, since it needs to look for revisions of the child model. Using this tweak,
the view of the actual child model is used, similar to the way the regular change and delete views are redirected.
django-guardian support
-----------------------
You can enable the content type of the base model to be used for the object levels permissions by setting the
django-guardian_ option `GUARDIAN_GET_CONTENT_TYPE` to `polymorphic.contrib.get_polymorphic_base_content_type`. Read
more about this option in the `django-guardian documentation <https://django-guardian.readthedocs.io/en/latest/configuration.html#guardian-get-content-type>`_.
.. _django-reversion: https://github.com/etianen/django-reversion
.. _django-reversion-compare: https://github.com/jedie/django-reversion-compare
.. _django-mptt: https://github.com/django-mptt/django-mptt
.. _django-polymorphic-tree: https://github.com/django-polymorphic/django-polymorphic-tree
.. _django-guardian: https://github.com/django-guardian/django-guardian