[Django's forms framework](https://docs.djangoproject.com/en/stable/topics/forms/) can be used within Wagtail admin views just like in any other Django app. However, Wagtail also provides various admin-specific form widgets, such as date/time pickers and choosers for pages, documents, images and snippets. By constructing forms using `wagtail.admin.forms.models.WagtailAdminModelForm` as the base class instead of `django.forms.models.ModelForm`, the most appropriate widget will be selected for each model field. For example, given the model and form definition:
```python
from django.db import models
from wagtail.admin.forms.models import WagtailAdminModelForm
the `date` and `image` fields on the form will use a date picker and image chooser widget respectively.
## Defining admin form widgets
If you have implemented a form widget of your own, you can configure `WagtailAdminModelForm` to select it for a given model field type. This is done by calling the `wagtail.admin.forms.models.register_form_field_override` function, typically in an `AppConfig.ready` method.
Specify a set of options that will override the form field's defaults when ``WagtailAdminModelForm`` encounters a given model field type.
:param model_field_class: Specifies a model field class, such as ``models.CharField``; the override will take effect on fields that are instances of this class.
:param to: For ``ForeignKey`` fields, indicates the model that the field must point to for the override to take effect.
:param override: A dict of keyword arguments to be passed to the form field's ``__init__`` method, such as ``widget``.
:param exact_class: If true, the override will only take effect for model fields that are of the exact type given by ``model_field_class``, and not a subclass of it.
```
For example, if the app `wagtail.videos` implements a `Video` model and a `VideoChooser` form widget, the following AppConfig definition will ensure that `WagtailAdminModelForm` selects `VideoChooser` as the form widget for any foreign keys pointing to `Video`:
```python
from django.apps import AppConfig
from django.db.models import ForeignKey
class WagtailVideosAppConfig(AppConfig):
name = 'wagtail.videos'
label = 'wagtailvideos'
def ready(self):
from wagtail.admin.forms.models import register_form_field_override
Wagtail's edit views for pages, snippets and ModelAdmin use `WagtailAdminModelForm` as standard, so this change will take effect across the Wagtail admin; a foreign key to `Video` on a page model will automatically use the `VideoChooser` widget, with no need to specify this explicitly.
Panels (also known as edit handlers until Wagtail 3.0) are Wagtail's mechanism for specifying the content and layout of a model form without having to write a template. They are used for the editing interface for pages and snippets, as well as the [ModelAdmin](/reference/contrib/modeladmin/index) and [site settings](/reference/contrib/settings) contrib modules.
See [](/reference/pages/panels) for the set of panel types provided by Wagtail. All panels inherit from the base class `wagtail.admin.panels.Panel`. A single panel object (usually `ObjectList` or `TabbedInterface`) exists at the top level and is the only one directly accessed by the view code; panels containing child panels inherit from the base class `wagtail.admin.panels.PanelGroup` and take care of recursively calling methods on their child panels where appropriate.
A view performs the following steps to render a model form through the panels mechanism:
* The top-level panel object for the model is retrieved. Usually this is done by looking up the model's `edit_handler` property and falling back on an `ObjectList` consisting of children given by the model's `panels` property. However, it may come from elsewhere - for example, the ModelAdmin module allows defining it on the ModelAdmin configuration object.
* The view calls `bind_to_model` on the top-level panel, passing the model class, and this returns a clone of the panel with a `model` property. As part of this process the `on_model_bound` method is invoked on each child panel, to allow it to perform additional initialisation that requires access to the model (for example, this is where `FieldPanel` retrieves the model field definition).
* The view then calls `get_form_class` on the top-level panel to retrieve a ModelForm subclass that can be used to edit the model. This proceeds as follows:
- Retrieve a base form class from the model's `base_form_class` property, falling back on `wagtail.admin.forms.WagtailAdminModelForm`
- Call `get_form_options` on each child panel - which returns a dictionary of properties including `fields` and `widgets` - and merge the results into a single dictionary
- Construct a subclass of the base form class, with the options dict forming the attributes of the inner `Meta` class.
* An instance of the form class is created as per a normal Django form view.
* The view then calls `get_bound_panel` on the top-level panel, passing `instance`, `form` and `request` as keyword arguments. This returns a `BoundPanel` object, which follows [the template component API](/extending/template_components). Finally, the `BoundPanel` object (and its media definition) is rendered onto the template.
