PolymorphicView

The crud_views_polymorphic package adds support for django-polymorphic models. It provides a two-step create flow (select subtype → fill form) and polymorphic-aware detail, update, and delete views that resolve the correct form based on the actual subtype of each object.

Installation

Install the polymorphic optional dependency group:

pip install django-crud-views[polymorphic]

Add the required apps to INSTALLED_APPS:

INSTALLED_APPS = [
    ...
    "polymorphic",
    "crud_views_polymorphic.apps.CrudViewsPolymorphicConfig",
    ...
]

Basic Usage

1. Define the model

Inherit from PolymorphicModel for the base class and define concrete subtypes:

from django.db import models
from polymorphic.models import PolymorphicModel


class Vehicle(PolymorphicModel):
    name = models.CharField(max_length=128)


class Car(Vehicle):
    doors = models.IntegerField()


class Truck(Vehicle):
    payload_tons = models.FloatField()

2. Define the ViewSet and views

from django.forms import modelform_factory

from crud_views.lib.viewset import ViewSet
from crud_views.lib.crispy import CrispyModelViewMixin
from crud_views.lib.crispy.form import CrispyDeleteForm
from crud_views_polymorphic.lib import (
    PolymorphicCreateViewPermissionRequired,
    PolymorphicCreateSelectViewPermissionRequired,
    PolymorphicUpdateViewPermissionRequired,
    PolymorphicDetailViewPermissionRequired,
)
from crud_views_polymorphic.lib.create_select import PolymorphicContentTypeForm
from crud_views_polymorphic.lib.delete import PolymorphicDeleteViewPermissionRequired

from .models import Vehicle, Car, Truck

cv_vehicle = ViewSet(model=Vehicle, name="vehicle")

CarForm = modelform_factory(Car, fields=["name", "doors"])
TruckForm = modelform_factory(Truck, fields=["name", "payload_tons"])


class VehicleCreateSelectView(CrispyModelViewMixin, PolymorphicCreateSelectViewPermissionRequired):
    form_class = PolymorphicContentTypeForm
    cv_viewset = cv_vehicle


class VehicleCreateView(CrispyModelViewMixin, PolymorphicCreateViewPermissionRequired):
    cv_viewset = cv_vehicle
    polymorphic_forms = {
        Car: CarForm,
        Truck: TruckForm,
    }


class VehicleUpdateView(CrispyModelViewMixin, PolymorphicUpdateViewPermissionRequired):
    cv_viewset = cv_vehicle
    polymorphic_forms = {
        Car: CarForm,
        Truck: TruckForm,
    }


class VehicleDeleteView(CrispyModelViewMixin, PolymorphicDeleteViewPermissionRequired):
    form_class = CrispyDeleteForm
    cv_viewset = cv_vehicle


class VehicleDetailView(PolymorphicDetailViewPermissionRequired):
    cv_viewset = cv_vehicle
    cv_property_display = [
        {"title": "Attributes", "properties": ["name"]},
    ]

3. Register URLs

# urls.py
urlpatterns = cv_vehicle.urlpatterns

4. Add the create_select action to the list view

from crud_views.lib.views import ListViewPermissionRequired, ListViewTableMixin

class VehicleListView(ListViewTableMixin, ListViewPermissionRequired):
    cv_viewset = cv_vehicle
    cv_list_actions = ["detail", "update", "delete"]
    cv_context_actions = ["create_select"]

View Classes

Class	Permission
PolymorphicCreateSelectView	—
PolymorphicCreateSelectViewPermissionRequired	add
PolymorphicCreateView	—
PolymorphicCreateViewPermissionRequired	add
PolymorphicUpdateView	—
PolymorphicUpdateViewPermissionRequired	change
PolymorphicDeleteView	—
PolymorphicDeleteViewPermissionRequired	delete
PolymorphicDetailView	—
PolymorphicDetailViewPermissionRequired	view

Two-step create flow

Creating a polymorphic instance requires two steps:

1. create_select — PolymorphicCreateSelectView renders a form with a ChoiceField of all registered subtypes. On submit it redirects to the create URL, passing polymorphic_ctype_id as a URL parameter.

2. create — PolymorphicCreateView reads polymorphic_ctype_id from the URL, resolves the subtype model via the content-type framework, and renders the matching form from polymorphic_forms.

Filtering available subtypes

PolymorphicCreateSelectView supports filtering which subtypes appear in the select form:

Attribute	Type	Description
cv_polymorphic_exclude	list[type] or None	Subtypes to hide from the select form
cv_polymorphic_include	list[type] or None	Only these subtypes appear in the select form

Only one of the two may be set at a time (enforced by system check E220).

polymorphic_forms

Set polymorphic_forms on PolymorphicCreateView and PolymorphicUpdateView to a dict that maps each subtype model class to its form class:

polymorphic_forms = {
    Car: CarForm,
    Truck: TruckForm,
}

The correct form is selected at runtime based on the resolved subtype.

System checks

ID	View	What is checked
E220	PolymorphicCreateSelectView	At most one of cv_polymorphic_exclude / cv_polymorphic_include is set