bgneal@202: """Signals for the weblinks application.
bgneal@202: We use signals to compute the denormalized category counts whenever a weblink
bgneal@202: is saved."""
bgneal@202: from django.db.models.signals import post_save
bgneal@202: from django.db.models.signals import post_delete
bgneal@202: 
bgneal@202: from weblinks.models import Category, Link
bgneal@202: 
bgneal@202: 
bgneal@202: def on_link_save(sender, **kwargs):
bgneal@202:     """This function updates the count field for all categories.
bgneal@202:     It is called whenever a link is saved via a signal.
bgneal@202:     """
bgneal@202:     if kwargs['created']:
bgneal@202:         # we only have to update the parent category
bgneal@202:         link = kwargs['instance']
bgneal@202:         cat = link.category
bgneal@202:         cat.count = Link.public_objects.filter(category=cat).count()
bgneal@202:         cat.save()
bgneal@202:     else:
bgneal@202:         # update all categories just to be safe (an existing link could
bgneal@202:         # have been moved from one category to another
bgneal@202:         cats = Category.objects.all()
bgneal@202:         for cat in cats:
bgneal@202:             cat.count = Link.public_objects.filter(category=cat).count()
bgneal@202:             cat.save()
bgneal@202: 
bgneal@202: 
bgneal@202: def on_link_delete(sender, **kwargs):
bgneal@202:     """This function updates the count field for the link's parent
bgneal@202:     category. It is called when a link is deleted via a signal.
bgneal@202:     """
bgneal@202:     # update the parent category
bgneal@202:     link = kwargs['instance']
bgneal@202:     cat = link.category
bgneal@202:     cat.count = Link.public_objects.filter(category=cat).count()
bgneal@202:     cat.save()
bgneal@202: 
bgneal@202: 
bgneal@202: post_save.connect(on_link_save, sender=Link)
bgneal@202: post_delete.connect(on_link_delete, sender=Link)