Django admin integration¶
Of course, it’s possible to register individual polymorphic models in the Django admin interface. However, to use these models in a single cohesive interface, some extra base classes are available.
Both the parent model and child model need to have a
The shared base model should use the
PolymorphicParentModelAdmin as base class.
The admin class for every child model should inherit from
base_modelshould be set.
Although the child models are registered too, they won’t be shown in the admin index page.
This only happens when
show_in_index is set to
The parent admin is only used for the list display of models, and for the edit/delete view of non-subclassed models.
All other model types are redirected to the edit/delete/history view of the child model admin. Hence, the fieldset configuration should be placed on the child admin.
When the child admin is used as base class for various derived classes, avoid using
Instead, use the
This allows the
to detect any additional fields in case the child model is overwritten.
Changed in version 1.0: It’s now needed to register the child model classes too.
In django-polymorphic 0.9 and below, the
child_models was a tuple of a
The admin classes were registered in an internal class, and kept away from the main admin site.
This caused various subtle problems with the
ManyToManyField and related field wrappers,
which are fixed by registering the child admin classes too. Note that they are hidden from
the main view, unless
show_in_index is set.
The models are taken from Advanced features.
from django.contrib import admin from polymorphic.admin import PolymorphicParentModelAdmin, PolymorphicChildModelAdmin, PolymorphicChildModelFilter from .models import ModelA, ModelB, ModelC, StandardModel class ModelAChildAdmin(PolymorphicChildModelAdmin): """ Base admin class for all child models """ base_model = ModelA # Optional, explicitly set here. # By using these `base_...` attributes instead of the regular ModelAdmin `form` and `fieldsets`, # the additional fields of the child models are automatically added to the admin form. base_form = ... base_fieldsets = ( ... ) @admin.register(ModelB) class ModelBAdmin(ModelAChildAdmin): base_model = ModelB # Explicitly set here! # define custom features here @admin.register(ModelC) class ModelCAdmin(ModelBAdmin): base_model = ModelC # Explicitly set here! show_in_index = True # makes child model admin visible in main admin site # define custom features here @admin.register(ModelA) class ModelAParentAdmin(PolymorphicParentModelAdmin): """ The parent model admin """ base_model = ModelA # Optional, explicitly set here. child_models = (ModelB, ModelC) list_filter = (PolymorphicChildModelFilter,) # This is optional.
Filtering child types¶
Child model types can be filtered by adding a
list_filter attribute. See the example above.
New in version 1.0.
Inline models are handled via a special
For models with a generic foreign key, there is a
GenericStackedPolymorphicInline class available.
When the inline is included to a normal
make sure the
PolymorphicInlineSupportMixin is included.
This is not needed when the admin inherits from the
In the following example, the
PaymentInline supports several types.
These are defined as separate inline classes.
The child classes can be nested for clarity, but this is not a requirement.
from django.contrib import admin from polymorphic.admin import PolymorphicInlineSupportMixin, StackedPolymorphicInline from .models import Order, Payment, CreditCardPayment, BankPayment, SepaPayment class PaymentInline(StackedPolymorphicInline): """ An inline for a polymorphic model. The actual form appearance of each row is determined by the child inline that corresponds with the actual model type. """ class CreditCardPaymentInline(StackedPolymorphicInline.Child): model = CreditCardPayment class BankPaymentInline(StackedPolymorphicInline.Child): model = BankPayment class SepaPaymentInline(StackedPolymorphicInline.Child): model = SepaPayment model = Payment child_inlines = ( CreditCardPaymentInline, BankPaymentInline, SepaPaymentInline, ) @admin.register(Order) class OrderAdmin(PolymorphicInlineSupportMixin, admin.ModelAdmin): """ Admin for orders. The inline is polymorphic. To make sure the inlines are properly handled, the ``PolymorphicInlineSupportMixin`` is needed to """ inlines = (PaymentInline,)
Using polymorphic models in standard inlines¶
To add a polymorphic child model as an Inline for another model, add a field to the inline’s
formed by the lowercased name of the polymorphic parent model with the string
_ptr appended to it.
Otherwise, trying to save that model in the admin will raise an AttributeError with the message “can’t set attribute”.
from django.contrib import admin from .models import StandardModel class ModelBInline(admin.StackedInline): model = ModelB fk_name = 'modelb' readonly_fields = ['modela_ptr'] @admin.register(StandardModel) class StandardModelAdmin(admin.ModelAdmin): inlines = [ModelBInline]
The polymorphic admin interface works in a simple way:
- The add screen gains an additional step where the desired child model is selected.
- The edit screen displays the admin interface of the child model.
- The list screen still displays all objects of the base class.
The polymorphic admin is implemented via a parent admin that redirects the edit and delete views
ModelAdmin of the derived child model. The list page is still implemented by the parent model admin.
The parent model¶
The parent model needs to inherit
PolymorphicParentModelAdmin, and implement the following:
The exact implementation can depend on the way your module is structured.
For simple inheritance situations,
child_models is the best solution.
For large applications,
get_child_models() can be used to query a plugin registration system.
By default, the non_polymorphic() method will be called on the queryset, so only the Parent model will be provided to the list template. This is to avoid the performance hit of retrieving child models.
This can be controlled by setting the
polymorphic_list property on the
parent admin. Setting it to True will provide child models to the list template.
Note: If you are using non-integer primary keys in your model, you have to edit
pk_regex = '([\w-]+)' if you use UUIDs. Otherwise you cannot change model entries.
The child models¶
- It corrects the breadcrumbs in the admin pages.
- It extends the template lookup paths, to look for both the parent model and child model in the
- It allows to set
base_formso the derived class will automatically include other fields in the form.
- It allows to set
base_fieldsetsso the derived class will automatically display any extra fields.
- Although it must be registered with admin site, by default it’s hidden from admin site index page.
This can be overriden by adding
Truein admin class.