|Version 3 (modified by Tyson Tate <tyson@…>, 10 years ago) (diff)|
What Are Signals?
Signals allow you to make Django call custom methods after common actions using a dispatcher. Beyond that, I really don't know much else. Please help expand this documentation, if you can.
The author of Zyons talks about signals a bit here.
Django has the following build in signalers:
All the above are related to classes in your models.py files.
You can send custom signals from the dispatcher, as well. In the following example from this intro to signals, a signal called "object_viewed" is sent whenever the following bit is called:
dispatcher.send(signal=signals.object_viewed, request=request, object=object)
You'll have to instantiate the signal in a file called "signals.py" in your app's folder:
The following is taken from Zyons, the only place I've seen signals used so far. Unless I'm completely incorrect, the following code has the dispatcher call "increment_tag_summary" before a TagUserObject object is saved, and "decrement_tag_summary" after a TagUserObject object is deleted.
from django.db.models import signals from django.dispatch import dispatcher [...] def increment_tag_summary(sender, instance, signal, *args, **kwargs): [...] def decrement_tag_summary(sender, instance, signal, *args, **kwargs): [...] dispatcher.connect( increment_tag_summary , signal=signals.pre_save, sender=TagUserObject ) dispatcher.connect( decrement_tag_summary , signal=signals.post_delete, sender=TagUserObject )