How to Use a Subscriber Decorator in a Class to Utilize Class Functionality?

[Atanusaha143]

I'm working on a Python application where I need to process messages from a stream using a subscriber. I want to encapsulate the subscriber logic within a class so I can use class functionalities like helper methods and instance variables using self.

Here's a simplified example of my current implementation:

class Subscriber:
    @nats_broker.subscriber(
        subject="some_subject_name",
        stream="some_stream_name",
        durable="some_consumer_name",
        pull_sub=PullSub(batch=True, batch_size=5),
        no_ack=True, 
        retry=True,
    )
    async def handle_subscriber(self, msg: NatsMessage, logger: Logger):
        try:
            logger.info("Started processing requests for 'some_subject_name'.")

            decoded_messages = Subscriber._decode_messages(msg=msg)
            logger.debug(f"Decoded messages: {decoded_messages}")

            message_dtos = Subscriber._map_message_dtos(decoded_messages=decoded_messages)
            logger.debug(f"Mapped message DTOs: {message_dtos}")

            await msg.ack()
            logger.info("Successfully processed requests.")
        except Exception as e:
            logger.error("An exception occurred during processing requests.", exc_info=e)
            await msg.nack()

    @staticmethod
    def _decode_messages(msg: NatsMessage):
        decoded_messages: list = []
        for message in msg.body:
            decoded_message = json.loads(message.decode("utf-8"))
            decoded_messages.append(decoded_message)
        return decoded_messages

    @staticmethod
    def _map_message_dtos(decoded_messages):
        pass

Issue:

I want to refactor this code so that I can call the class methods using self rather than Subscriber.method_name(...). For example:

decoded_messages = self._decode_messages(msg=msg)

The current implementation using the decorator @nats_broker.subscriber doesn't provide access to self

Question:

Are there any best practices or alternative patterns I should consider for encapsulating subscriber logic while ensuring access to instance-level methods and variables? Additionally, I want to ensure that dependency injection is properly initialized through the class constructor (__init__).

[Lancetnik]

The current implementation using the decorator @nats_broker.subscriber doesn't provide access to self

Subscriber can't provide to access to self due your didn't create a class instance - you registered class method as a subscriber handler. So support class-based case you can use static or class methods as a subscriber handler or register handler something like that:

subscriber_obj = Subscriber()

broker.subscruber(subscriber_obj.handle_msg)

Anyway, I don't recommend you to use class-based handlers and prefer any existing mechanisms like Context/Depends