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annotate weblinks/signals.py @ 794:f416f5db3d91
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| author | Brian Neal <bgneal@gmail.com> |
|---|---|
| date | Tue, 27 May 2014 15:06:38 -0500 |
| parents | ee87ea74d46b |
| children |
| rev | line source |
|---|---|
| bgneal@202 | 1 """Signals for the weblinks application. |
| bgneal@202 | 2 We use signals to compute the denormalized category counts whenever a weblink |
| bgneal@202 | 3 is saved.""" |
| bgneal@202 | 4 from django.db.models.signals import post_save |
| bgneal@202 | 5 from django.db.models.signals import post_delete |
| bgneal@202 | 6 |
| bgneal@202 | 7 from weblinks.models import Category, Link |
| bgneal@202 | 8 |
| bgneal@202 | 9 |
| bgneal@202 | 10 def on_link_save(sender, **kwargs): |
| bgneal@202 | 11 """This function updates the count field for all categories. |
| bgneal@202 | 12 It is called whenever a link is saved via a signal. |
| bgneal@202 | 13 """ |
| bgneal@202 | 14 if kwargs['created']: |
| bgneal@202 | 15 # we only have to update the parent category |
| bgneal@202 | 16 link = kwargs['instance'] |
| bgneal@202 | 17 cat = link.category |
| bgneal@202 | 18 cat.count = Link.public_objects.filter(category=cat).count() |
| bgneal@202 | 19 cat.save() |
| bgneal@202 | 20 else: |
| bgneal@202 | 21 # update all categories just to be safe (an existing link could |
| bgneal@202 | 22 # have been moved from one category to another |
| bgneal@202 | 23 cats = Category.objects.all() |
| bgneal@202 | 24 for cat in cats: |
| bgneal@202 | 25 cat.count = Link.public_objects.filter(category=cat).count() |
| bgneal@202 | 26 cat.save() |
| bgneal@202 | 27 |
| bgneal@202 | 28 |
| bgneal@202 | 29 def on_link_delete(sender, **kwargs): |
| bgneal@202 | 30 """This function updates the count field for the link's parent |
| bgneal@202 | 31 category. It is called when a link is deleted via a signal. |
| bgneal@202 | 32 """ |
| bgneal@202 | 33 # update the parent category |
| bgneal@202 | 34 link = kwargs['instance'] |
| bgneal@202 | 35 cat = link.category |
| bgneal@202 | 36 cat.count = Link.public_objects.filter(category=cat).count() |
| bgneal@202 | 37 cat.save() |
| bgneal@202 | 38 |
| bgneal@202 | 39 |
| bgneal@260 | 40 post_save.connect(on_link_save, sender=Link, dispatch_uid='weblinks.signals') |
| bgneal@260 | 41 post_delete.connect(on_link_delete, sender=Link, dispatch_uid='weblinks.signals') |