Django: Cascade deletion to related one-to-one fields

README.rst

Django: Cascade deletion to related one-to-one fields

This gist assumes that an app named base exists and is included in INSTALLED_APPS via base.apps.BaseConfig.

base.utils.delete_related_onetoonefield works by looping thru the model instance's available fields and deleting all non-null django.db.models.fields.related.OneToOneField instances.

apps.py

from django.apps import AppConfig


class BaseConfig(AppConfig):
    name = 'base'
    verbose_name = 'Base'

    def ready(self):
        import base.signals  # noqa

models.py

from django.db import models


class OneToOneRequiredModel(models.Model):
    value = models.CharField(max_length=255)


class OneToOneOptionalModel(models.Model):
    value = models.CharField(max_length=255)


class BaseModel(models.Model):
   one_to_one_required = models.OneToOneField(OneToOneRequiredModel, on_delete=models.SET_CASCADE)
   one_to_one_optional = models.OneToOneField(OneToOneOptionalModel, null=True, blank=True, on_delete=models.SET_NULL)

signals.py

from base.models import BaseModel
from base.utils import delete_related_onetoonefield


@receiver(pre_delete, sender=Application)
def delete_base_cascade_onetoonefields(sender, instance, using, **kwargs):
    """
    Cascade 'BaseModel' model deletion to OneToOneField fields
    """
    delete_related_onetoonefield(instance)

utils.py

from django.db.models.fields.related import OneToOneField


def delete_related_onetoonefield(instance):
    """
    Helper function to cascade deletion to related.OneToOneField fields from a model instance
    """
    for field in type(instance)._meta.get_fields():
        if isinstance(field, OneToOneField):
            try:
                getattr(instance, field.name).delete()
            except AttributeError:
                # Field is of null value
                pass