Using django signals in channels consumer classes : <p>I am trying to develop an auction type system, where a customer makes an order, and then different stores can offer a price for that order. </p>

<p>An interesting part of this system is that when the order is initially created, the available stores will have 60 seconds to make their respective offer. When a first store makes their offer, the "auction" will now only have the next 20 seconds for other stores to make their own offer. If they do make another offer, in this smaller allocated time, then this 20 second is refreshed. Offers can keep on being received as long as there is enough time, which cannot surpass the initial 60 seconds given.</p>

<pre><code>class Order(models.Model):
    customer = models.ForeignKey(Customer)
    create_time = models.DateTimeField(auto_now_add=True)
    update_time = models.DateTimeField(auto_now_add=True)
    total = models.FloatField(default=0)
    status = models.IntegerField(default=0)
    delivery_address = models.ForeignKey(DeliveryAddress)
    store = models.ForeignKey(Store, null=True, blank=True, related_name='orders', on_delete=models.CASCADE)
    credit_card = models.ForeignKey(CreditCard, null=True, blank=True, related_name='orders')

class OrderOffer(models.Model):
    store = models.ForeignKey(Store, related_name="offers", on_delete=models.CASCADE)
    order = models.ForeignKey(Order, related_name="offers", on_delete=models.CASCADE)
    create_time = models.DateTimeField(auto_now_add=True)
</code></pre>

<p>Besides these requirements, I also want to update the client when new offers arrive in real-time. For this, I'm using <code>django-channels</code> implementation of WebSockets.</p>

<p>I have the following <code>consumers.py</code>file:</p>

<pre><code>from channels.generic.websockets import WebsocketConsumer
from threading import Timer
from api.models import Order, OrderOffer
from django.db.models.signals import post_save
from django.dispatch import receiver

class OrderConsumer(WebsocketConsumer):

    def connect(self, message, **kwargs):
        """
        Initialize objects here.
        """
        order_id = int(kwargs['order_id'])
        self.order = Order.objects.get(id=order_id)
        self.timer = Timer(60, self.sendDone)
        self.timer.start()
        self.message.reply_channel.send({"accept": True})

    def sendDone(self):
        self.send(text="Done")

    # How do I bind self to onOffer?
    @receiver(post_save, sender=OrderOffer)
    def onOffer(self, sender, **kwargs):
        self.send(text="Offer received!")
        if (len(self.offers) == 0):
            self.offerTimer = Timer(20, self.sendDone)
            self.offers = [kwargs['instance'],]
        else:
            self.offerTimer = Timer(20, self.sendDone)

        self.offers.append(kwargs['instance'])


    def receive(self, text=None, bytes=None, **kwargs):
        # Echo
        self.send(text=text, bytes=bytes)

    def disconnect(self, message, **kwargs):
        """
        Perform necessary disconnect operations.
        """
        pass
</code></pre>

<p>I have successfully been able to establish a WebSocket communication channel between my client and the server. I've tested sending messages, and everything seems ok. Now I want to detect the creation of new <code>OrderOffer</code>'s, and send a notification to the client. For this, I need access to the <code>self</code> variable, to use <code>self.send</code>, which is impossible, as the signals decorator does not send this parameter. I've tried forcing it by declaring onOffer with self, but I get the following error:</p>

<p><code>TypeError: onOffer() missing 1 required positional argument: 'self'</code></p>

<p>If I could somehow access the keyword arguments, that signals sets, I could maybe do something like:
<code>context = self</code>.</p>

<p>I would appreciate any help, or even alternative solutions to my original problem.</p>
