Fields and Widgets

Contents:

Model fields

JSONField

class JSONField(schema=None, pre_save_hook=None, **options)

New in version 2.0.

It is basically a subclass of Django’s JSONField, but for convenience, it automatically sets up the JSON editor widget for you.

In Django < 3.1, for databases other than Postgres, it uses a TextField underneath.

schema: dict, callable

A dict or a callable object specifying the schema for the current field.

A callable is useful for specifying dynamic choices.

The callable function may optionally receive the current model instance. See: Accessing model instance in callable schema.

Changed in version 2.1: The ability to provide a callable was added.

Changed in version 2.8: Callable schema may receive an instance argument.

pre_save_hook: callable

New in version 2.10.

(Optional) Sometimes you may wish to transform the JSON data before saving in the database.

For that purpose, you can provide a callable through this argument which will be called before saving the field’s value in the database.

The pre_save_hook callable will receive the current value of the field as the only argument. It must return the value which you intend to save in the database.

def pre_save_hook(value):
    # do something with the value ...
    return value


class MyModel(...):
    items = JSONField(schema=..., pre_save_hook=pre_save_hook)
**options

This JSONField accepts all the arguments accepted by Django’s JSONField, such as a custom encoder or decoder.

For details about other parameters, options and attributes of the JSONField, see Django’s docs.

Usage:

from django_jsonform.models.fields import JSONField


class MyModel(models.Model):
    ITEMS_SCHEMA = {...}

    items = JSONField(schema=ITEMS_SCHEMA)

ArrayField

class ArrayField(base_field, size=None, **options)

New in version 2.0.

A subclass of Django’s ArrayField except it renders a dynamic form widget.

It takes exactly the same arguments as the original class.

It also supports multiple levels of array nesting.

Usage:

from django_jsonform.models.fields import ArrayField


class MyModel(models.Model):
    items = ArrayField(models.CharField(max_length=50), size=10)
    # ...

For more details, see Django’s docs.

Widgets

JSONFormWidget

class JSONFormWidget(schema, model_name='')

The widget which renders the editor.

It can be used in a form if you don’t want to use the model field.

schema: dict, callable

A dict or a callable object specifying the schema for the current field.

A callable is useful for specifying dynamic choices.

The callable function may optionally receive the current model instance. See: Accessing model instance in callable schema.

Changed in version 2.1: The ability to provide a callable was added.

Changed in version 2.8: Callable schema may receive an instance argument.

model_name: str

An optional string. The name of the model. It is passed to the file upload handler so that you can identify which model is requesting the file upload.

See Additional request parameters for more details.

Usage:

# admin.py

from django_jsonform.widgets import JSONFormWidget
from myapp.models import ShoppingList


class ShoppingListForm(forms.ModelForm):
    model = ShoppingList
    fields = '__all__'
    widgets = {
        'items': JSONFormWidget(schema=ShoppingList.ITEMS_SCHEMA)
    }

class ShoppingListAdmin(admin.ModelAdmin):
    form = ShoppingListForm

admin.site.register(ShoppingList, ShoppingListAdmin)

This widget can not be used directly with Django’s ArrayField because Django’s ArrayField converts the value from array to a string before passing it to the widget whereas it expects a list or a dict.

Accessing model instance in callable schema

New in version 2.8.

Automatically accessing model instance in a widget is not possible. This is due the way Django initialises the widgets and form fields.

However, you can bypass this limitation by manually setting an instance attribute on the widget.

def callable_schema(instance):
    # ... do something ...
    pass

class MyModel(models.Model):
    json_field = JSONField(schema=callable_schema)


# create a custom modelform
class MyModelForm(forms.ModelForm):
    def __init__(self):
        # manually set the current instance on the widget
        self.fields['json_field'].widget.instance = self.instance


# set the form on the admin class
class MyAdmin(admin.ModelAdmin):
    form = MyModelForm

Now, the value of the instance will be passed to your callable schema function.