Observer model instance

This mixin consumer lets you subscribe to all changes of a specific instance and gives you access to the retrieve action.

# serializers.py
from rest_framework import serializers
from django.contrib.auth.models import User

class UserSerializer(serializers.ModelSerializer):

    class Meta:
        model = User
        fields = ["id", "username", "email", "password"]
        extra_kwargs = {'password': {'write_only': True}}

    def create(self, validated_data):
        user = User(
            email=validated_data['email'],
            username=validated_data['username']
        )
        user.set_password(validated_data['password'])
        user.save()
        return user

# consumers.py
from django.contrib.auth.models import User
from .serializers import UserSerializer
from djangochannelsrestframework.generics import GenericAsyncAPIConsumer
from djangochannelsrestframework.observer.generics import ObserverModelInstanceMixin

class UserConsumer(ObserverModelInstanceMixin, GenericAsyncAPIConsumer):
    queryset = User.objects.all()
    serializer_class = UserSerializer

# routing.py
from django.urls import re_path
from . import consumers

websocket_urlpatterns = [
    re_path(r"^ws/$", consumers.UserConsumer.as_asgi()),
]

How to use it

First, we will create the web socket instance in javascript.

const ws = new WebSocket("ws://localhost:8000/ws/")

ws.onmessage = function(e){
    console.log(e)
}

Note

We must have a few users in our database for testing, if not, create them.

Retrieve action.

ws.send(JSON.stringify({
    action: "retrieve",
    request_id: new Date().getTime(),
    pk: 1,
}))
/* The return response will be something like this.
{
    "action": "list",
    "errors": [],
    "response_status": 200,
    "request_id": 1550050,
    "data": {'email': '1@example.com', 'id': 1, 'username': 'test 1'},
}
*/

Subscription

1. Subscribe to a specific instance.

ws.send(JSON.stringify({
    action: "retrieve",
    request_id: new Date().getTime(),
    pk: 1,
}))
/* After subscribing the response will be something like this.
{
    "action": "subscribe_instance",
    "errors": [],
    "response_status": 201,
    "request_id": 1550050,
    "data": null,
}
*/

2. Changing the model instance from the shell will fire the subscription event.

>>> from django.contrib.auth.models import User
>>> user = User.objects.get(pk=1)
>>> user.username = "edited user name"
>>> user.save()

3. After saving the model instance in the console, we will see the subscription message.

{
    action: "update",
    errors: [],
    response_status: 200,
    request_id: 1550050,
    data: {email: '1@example.com', id: 1, username: 'edited user name'},
}

Todo

• More detailed example.