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Django JSON form field on steroids using react-json-schema-form

Project description

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django-reactive integrates react-jsonschema-form (RJSF) in Django projects.

Motivation

JSON types is a cool feature of Postgres that allows combining both relational and non-relational approaches to storing data together. In most cases it would lead to a simpler database design.

The JSONField in Django provides a nice way of integrating json and jsonb Postgres types inside the ORM. ORM can even utilise JSON fields to perform database queries. jsonb type also offers indexing for JSON documents. That makes it a powerful tool in the application design and opens a wide range of use cases, e.g. polymorphic behaviour, storing complex hierarchies and lists of related entities.

However, the main limitation of JSONField in Django is that it does not offer a good way of managing such objects in the default admin UI. Defining JSON objects inside the textarea is not practical for most use cases. django-reactive tries to address this problem by offering an integration between JSONField and the awesome react-jsonschema-form (RJSF) JavaScript library. It also uses Python jsonschema <https://github.com/Julian/jsonschema> library for backend validation. Such integration from our practice can significantly reduce an amount of work you need to do to build custom forms for JSONField types.

In most cases developers would only need to define a JSON schema configuration for such field and optionally UI schema to modify UI for those forms.

A basic use case is demonstrated below:

from django.db import models

from django_reactive.fields import ReactJSONSchemaField


class Registration(models.Model):
    basic = ReactJSONSchemaField(
        help_text="Registration form",
        schema={
            "title": "Register now!",
            "description": "Fill out the form to register.",
            "type": "object",
            "required": [
                "firstName",
                "lastName"
            ],
            "properties": {
                "firstName": {
                    "type": "string",
                    "title": "First name"
                },
                "lastName": {
                    "type": "string",
                    "title": "Last name"
                },
                "age": {
                    "type": "integer",
                    "title": "Age"
                },
                "bio": {
                    "type": "string",
                    "title": "Bio"
                },
                "password": {
                    "type": "string",
                    "title": "Password",
                    "minLength": 3
                },
                "telephone": {
                    "type": "string",
                    "title": "Telephone",
                    "minLength": 10
                }
            }
        },
        ui_schema={
            "firstName": {
                "ui:autofocus": True,
                "ui:emptyValue": ""
            },
            "age": {
                "ui:widget": "updown",
                "ui:title": "Age of person",
                "ui:description": "(earthian year)"
            },
            "bio": {
                "ui:widget": "textarea"
            },
            "password": {
                "ui:widget": "password",
                "ui:help": "Hint: Make it strong!"
            },
            "date": {
                "ui:widget": "alt-datetime"
            },
            "telephone": {
                "ui:options": {
                    "inputType": "tel"
                }
            }
        },
    )

It will generate a form like this:

images/simple.png

Quick start

Install django-reactive:

pip install django-reactive

Add it to your INSTALLED_APPS:

INSTALLED_APPS = (
    ...
    'django_reactive',
    ...
)

Running the example

Build the docker image for the Django application in example/:

  • Run docker-compose up -d

This will automatically create the database, run migrations, import the default superuser, and run the Django development server on http://127.0.0.1:8000.

Django admin example

  • Open http://127.0.0.1:8000/admin/ and login with username admin and password test.
  • Go to the “Test models” admin section to see the example forms.

Normal Django view example

You will be redirected to the detail view of the created object after the form saves.

Usage outside of Django admin

To use outside of the Django admin, the following are required in the template:

  • A call to the form media property using {{ form.media }}
  • An HTML submit input with name=”_save”.
<!DOCTYPE html>
<html>
<head>
  <title>Homepage</title>
</head>
<body>
  {{ form.media }}
  <form method="post">
    {% csrf_token %}
    {{ form }}
    <input type="submit" value="Save" name="_save">
  </form>
</body>
</html>

Optional configuration

Schema fields accept the following parameters for additional configuration:

  • extra_css: Include additional static CSS files available in the widget.
  • extra_js: Include additional static JavaScript files available in the widget.
  • on_render: A python method to make dynamic schema modifications at render-time.

Extra CSS and JSS files should be accessible using Django’s staticfiles configurations and passed as a list of strings.

Render methods require both schema and ui_schema as arguments to allow dynamic schema modification when rendering the widget. An optional instance keyword argument may also be used for referencing an object instance (must be set on the widget in the form). This method does not return anything.

Example usage

The example below demonstrates a use-case in which the options available for a particular field may be dynamic and unavailable in the initial schema definition. These would be populated at render-time and made available in the form UI.

def set_task_types(schema, ui_schema):
    from todos.models import TaskType

    task_types = list(TaskType.objects.all().values_list("name", flat=True))
    schema["definitions"]["Task"]["properties"]["task_type"]["enum"] = task_types
    ui_schema["task_lists"]["items"]["tasks"]["items"]["task_type"][
        "ui:help"
    ] = f"Select 1 of {len(task_types)} task types"

class Todo(models.Model):
    """
    A collection of task lists for a todo.
    """

    name = models.CharField(max_length=255)
    task_lists = ReactJSONSchemaField(
        help_text="Task lists",
        schema=TODO_SCHEMA,
        ui_schema=TODO_UI_SCHEMA,
        on_render=set_task_types,
        extra_css=["css/extra.css"],
        extra_js=["js/extra.js"],
    )

Schema model form class

The form class ReactJSONSchemaModelForm (subclassed from Django’s ModelForm) can be used to provide the model form’s instance object to the schema field widgets:

from django_reactive.forms import ReactJSONSchemaModelForm
class MyModelForm(ReactJSONSchemaModelForm):
    ...

This allows the on_render method set for a schema field to reference the instance like this:

def update_the_schema(schema, ui_schema, instance=None):
    if instance and instance.some_condition:
        ui_schema["my_schema_prop"]["ui:help"] = "Some extra help text"

Features

  • React, RJSF and other JS assets are bundled with the package.
  • Integration with default Django admin theme.
  • Backend and frontend validation.
  • Configurable static media assets
  • Dynamic schema mutation in widget renders

Limitations

To implement this behaviour you can define an array schema with one property serving as a key of the object and do transformation in your JSON class. An example will be provided later.

Future development

  • Display description as tooltips
  • Polish styles and HTML generated by RJSF

Project details


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