Take advantage of Python class nesting to define existentially-dependent parent-child relationships!
Given the following model definition:
class Parent(models.Model):
class Child(models.Model):
...By applying the metaclass patch, the model Parent.Child will gain a not null, cascading, foreign key to Parent:
> Parent.Child._meta.get_fields()
(<django.db.models.fields.BigAutoField: id>,
<django.db.models.fields.related.ForeignKey: parent>)
> Parent.Child._meta.get_field('parent').null
False
> parent = Parent.objects.create()
> child = Parent.Child.objects.create(parent=parent)
> child.parent
<Parent: Parent object (1)>
> parent.delete()
(2, {'nested_models.Child': 1, 'nested_models.Parent': 1})
> child.refresh_from_db()
---------------------------------------------------------------------------
... <traceback omitted> ...
DoesNotExist: Child matching query does not exist.