GenericForeignKey fields¶

The GenericForeignKey field (GFK) is a great feature provided by Django’s django.contrib.contenttypes module. While a normal ForeignKey field can point to a database object of a given model, a GenericForeignKey can point to a database object of any model.

This section provides a topic overview. See also A tested example of GFK fields and test_broken_gfks).

Lino’s disable_delete method tests for related objects, which automatically includes also those which are related using a GFK. non-nullable and warning before message.

In order to use GFKs, you must have django.contrib.contenttypes in your INSTALLED_APPS. In a Lino application we recommend to use lino.modlib.contenttypes, which is a thin wrapper around Django’s original app. Lino’s version gives you additional functionality:

the Controllable model mixin
the BrokenGFKs table

In Lino you can configure the cascading behaviour from the model which defines the GFK, either by using the allow_cascaded_delete attribute or by defining a nullable GFK.