topic.py

# -*- coding: utf-8 -*-


class Topic(object):
    _receivers = {}

    def __init__(self, topic_name):
        self._topic_name = topic_name

    def subscribe(self, receiver):
        if not callable(receiver):
            raise ValueError('Receiver must be callable.')

        receivers = self._receivers.get(self._topic_name, [])
        receivers.append(receiver)
        self._receivers[self._topic_name] = receivers

    def publish(self, *args, **kwargs):
        receivers = self._receivers.get(self._topic_name, [])

        for receiver in receivers:
            receiver(*args, **kwargs)

    def unsubscribe(self, receiver):
        receivers = self._receivers.get(self._topic_name, [])
        receivers.remove(receiver)

    def empty(self):
        if self._topic_name in self._receivers:
            del self._receivers[self._topic_name]


def subscribe(topic_name):
    def wrap(receiver):
        Topic(topic_name).subscribe(receiver)
        return receiver
    return wrap