Subscribe to reverse Foreign Key changes

[joseluratm]

First of all, thank you very much for your work. It is a great library!

I am currently facing a casuistica that I do not know if it is because of bad implementation of mine, but I can not find the best solution.

I'll explain my case, to see if you can shed some light on my problem.

Right now I have the following models:

class customUser(AbstractUser):
    email = models.EmailField(max_length=50, unique=True)


class event(models.Model):
    title = models.CharField(max_length=200)
    assigned_to = models.ForeignKey(customUser, blank=False, on_delete=models.DO_NOTHING, related_name='assigned_user_case')

in my web front end, I can assign each of the events to different users. That is to say, a user can have many events assigned to him and an event can only be assigned to one user.

My goal is that I want to be able to be able to receive all signals from events that bind/unbind to a user filtering by the user. This means that only subscription and unsubscription updates per user are sent to each user.

I have tried using the filtering example you specify in the main readme of the project, but I am not able to get it to work. Also, I don't know if that example would be enough to do what I want.

Thank you very much for your help.

[hishnash]

Sorry it's taken so long to get back to you.

You will need to use a filtering based on the user pk.

class MyConsumer(AsyncAPIConsumer):

  @model_observer(models.event)
  async def event_change_handler(
      self,
      message,
      observer=None,
      action=None,
      subscribing_request_ids=[],
      **kwargs
  ):
      for request_id in subscribing_request_ids:
          await self.send_json(dict(body=message, action=action, request_id=request_id))

  @event_change_handler.groups_for_signal
  def classroom_change_handler(self, instance: models.event, **kwargs):
      # this block of code is called very often *DO NOT make DB QUERIES HERE*
      yield f'-user-event.{instance.assigned_to_id}'

  @event_change_handler.groups_for_consumer
  def event_change_handler(self, school=None,  user=None, **kwargs):
      # This is called when you subscribe/unsubscribe
     yield   f'-user-event.{user.id}'

  @action()
  async def subscribe_to_events(self, request_id, **kwargs):
      # check user has permission to do this
      await self.event_change_handler.subscribe(user=self.scope['user'], request_id=request_id)

This will mean when users subscribe they subscribe to all changes to event models that point to the user.

Note if an event model is updated to change the old user that as assigned will get a delete message and the new user will get a create message (since from their perspective the event has ben deleted or created not changed).

[hishnash]

Do you want user X to know that is was assigned to Y or just that is has now been unassigned from them?

[joseluratm]

Notify user X that the event has been unassigned

[hishnash]

The current implementation you have there should do this, user X should get notified that the 'event' as been deleted when it is assigned to a new user. Is that not happening for you?

[joseluratm]

It is not happening to me. Maybe it's some implementation problem on my part somewhere else in the code.

Anyway, thank you very much!!!

[hishnash]

are you able to share how you are changing the 'events' assigned user?

What should be happening is that the current user gets a message 'delete' (if they are subscribed when this change takes place). are you able to put a print statement in

  @model_observer(models.event)
  async def event_change_handler(
      self,
      message,
      observer=None,
      action=None,
      subscribing_request_ids=[],
      **kwargs
  ):
      for request_id in subscribing_request_ids:
          await self.send_json(dict(body=message, action=action, request_id=request_id))

Bringing out the message and action