GenericForeignKey
~~~~~~~~~~~~~~~~~

Model example
=============

Consider such a model:

.. code-block:: python

    from django.contrib.contenttypes.fields import GenericForeignKey
    from django.db import models


    class TestModel(models.Model):
        name = models.CharField(max_length=200)
        language = models.CharField(max_length=200)

        content_type = models.ForeignKey(
            'contenttypes.ContentType',
            null=True,
            blank=True,
            editable=False,
        )

        object_id = models.PositiveIntegerField(
            null=True,
            blank=True,
            editable=False,
        )

        location = GenericForeignKey('content_type', 'object_id')

        def __str__(self):
            return self.name

.. _generic-autocomplete-view:

Form example
============

To enable the use of automatic views we need to add 'dal_queryset_sequence'
 to :django:setting:`INSTALLED_APPS`.

First, we can't use Django's ModelForm because it doesn't support
non-editable fields, which GenericForeignKey is. Instead, we'll use
:py:class:`dal.forms.FutureModelForm`.

Then we need to add the
:py:class:`dal_select2_queryset_sequence.fields.Select2GenericForeignKeyModelField`
field, with model_choice as keyword: this is a list of tuple, with the models
you want in the autocompletion and the validation, and the value of the
attribute of the model you want to query in the widget searchbox. Optionally,
you can forward an existing field in the form to filter an attribute of the
model, by adding a list of tuple containing the field to forward and the value
to filter.  In this example, the text inserted in the language field will
filter the country models by their 'spoken_language'
attribute.

Result:

.. code-block:: python

    from dal import autocomplete  # don't forget to pip install django-querysetsequence

    class TestForm(autocomplete.FutureModelForm):

        location = autocomplete.Select2GenericForeignKeyModelField(
            # Model with values to filter, linked with the name field
            model_choice=[(Country, 'country_code', [('language', 'spoken_language'),]),
                          (City, 'name')],
        )

        class Meta:
            model = TestModel

If you want to use your own widgets and views, assuming the widget takes an url as argument
and the view takes a queryset in its "as_view()" method, you can use
:py:class:`~dal_queryset_sequence.fields.GenericForeignKeyModelField`:

.. code-block:: python

    from dal import autocomplete

    class TestForm(autocomplete.FutureModelForm):

        location = autocomplete.GenericForeignKeyModelField(
            model_choice=[(Country,), (City,)],  # Models
            widget=autocomplete.QuerySetSequenceSelect2,
            view=autocomplete.Select2QuerySetSequenceView,
        )

        class Meta:
            model = TestModel

In this example, we took :py:class:`~dal_select2_queryset_sequence.widgets.QuerySetSequenceSelect2` as the
custom widget and :py:class:`~dal_select2_queryset_sequence.views.Select2QuerySetSequenceView`.


Register the view for the form
==============================

In url.py:

.. code-block:: python

    from .forms import TestForm

    urlpatterns = [...]  # your regular url patterns
    urlpatterns.extend(TestForm.as_urls())

It will enable the search box to query and filter the results