Hey all —
I've been doing some thinking lately about how we handle events in Pinax. Let
me first define an event. An event is an occurrence of a voluntarily action.
Examples of these include:
* user A joined project B
* user A updated their avatar
* user A became friends with user B
Currently, we have blurred the line between an occurrence and action taken
from the occurrence. This is called django-notification. There is overlap
between the way we are handling this and something like an activity stream.
We have on-site notifications which try to emulate an activity stream, but
in my opinion fails horribly at it. Notifications must be sent to users. This
becomes problematic when the action you want to take is to notify an IRC
channel for example.
I'd like to propose a change. At this point this change won't be in
django-notification. Just replace its use as the event emitter. It had been
discussed in the past to use signals. I think this is a good use-case for
using them.
I see two direct benefits from this approach:
* don't need to enforce apps to optionally support django-notification
* listener code is project-level which can depend on anything the project does
(solves cases like when avatar is updated let all friends of the user know
they've updated their avatar)
To demostrate (code style below designed for brevity):
# django-avatar signals.py
import django.dispatch
avatar_updated = django.dispatch.Signal(providing_args=["user", "avatar"])
# django-avatar views.py
from avatar import signals
def change(request, ...):
... code that handles request and makes Avatar object
signals.avatar_updated.send(sender=request, user=request.user,
avatar=avatar)
... rest of view ...
# project-level app (no name decided yet, but working name is
request_events)
# handlers.py
from notification import models as notification
from friends.models import Friendship
def avatar_updated(sender, **kwargs):
request = sender
ctx = {
"user": kwargs.get("user"),
"avatar": kwargs.get("avatar"),
}
notification.send([request.user], "avatar_updated", ctx)
friends = f["friend"] for f in
Friendship.objects.friends_for_user(request.user)
notification.send(friends, "avatar_friend_updated", ctx)
# models.py
import avatar.signals
from request_events import handlers
avatar.signals.avatar_updated.connect(handlers.avatar_changed)
I'd like to gather thoughts from people. Based on the advantages
above this seems like a win to me. If we are in agreement with the direction
of this change I plan to integrate this at PyCon for 0.9 alpha.
Brian Rosner
http://oebfare.com
http://twitter.com/brosner
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