need more documents for groups_for_signal and groups_for_consumer, and what "__" means in the examples

[Randix6644]

what are groups_for_signal and groups_for_consumer for? I've read the documents but still have no clue about them.
And I don't get what " f'chat__{instance}'" means in the example, what does "__" mean in this case?

[hishnash]

@Randix6644 could you link to the example in question.

[johnthagen]

I assume @Randix6644 is referring to the examples in the README here:

• https://github.com/NilCoalescing/djangochannelsrestframework/blob/master/README.rst#subscribing-to-a-signal

# consumers.py
from djangochannelsrestframework.consumers import AsyncAPIConsumer
from djangochannelsrestframework.decorators import action
from djangochannelsrestframework.observer import observer
from rest_framework import status
from .signals import joined_chat_signal
from .serializers import UserSerializer


class TestConsumer(AsyncAPIConsumer):

    @action()
    def join_chat(self, chat_id, **kwargs):
        serializer = UserSerializer(instance=self.scope['user'])
        joined_chat_signal.send(sender='join_chat', data=serializer.data, **kwargs)
        return {}, status.HTTP_204_NO_CONTENT

    @observer(signal=joined_chat_signal)
    async def joined_chat_handler(self, data, observer=None, action=None, subscribing_request_ids=[], **kwargs):
        for request_id in subscribing_request_ids:
            await self.reply(action='joined_chat', data=data, status=status.HTTP_200_OK, request_id=request_id)

    @joined_chat_handler.serializer
    def join_chat_handler(self, sender, data, **kwargs): # the data comes from the signal.send and will be available in the observer
        return data

    @joined_chat_handler.groups_for_signal
    def joined_chat_handler(self, instance, **kwargs):
        yield f'chat__{instance}'

    @joined_chat_handler.groups_for_consumer
    def joined_chat_handler(self, chat, **kwargs):
        if chat:
            yield f'chat__{chat}'

    @action()
    async def subscribe_joined(self, chat_id, request_id, **kwargs):
        await self.joined_chat_handler.subscribe(chat_id, request_id=request_id)

[hishnash]

@Randix6644 sorry of the slow response

the __ has not magical meaning it is just there for readability you can use anything you like. Whatever you provide here is in the end hashed to ensure it fits within the length constraints of the channel layer you are using.