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bgneal@921
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1 """Signal handlers for the weblinks application.
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bgneal@921
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2
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bgneal@202
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3 We use signals to compute the denormalized category counts whenever a weblink
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bgneal@921
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4 is saved.
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bgneal@921
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5 """
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bgneal@202
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6 from django.db.models.signals import post_save
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bgneal@202
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7 from django.db.models.signals import post_delete
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bgneal@202
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8
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bgneal@202
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9 from weblinks.models import Category, Link
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bgneal@202
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10
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bgneal@202
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11
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bgneal@202
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12 def on_link_save(sender, **kwargs):
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bgneal@202
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13 """This function updates the count field for all categories.
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bgneal@202
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14 It is called whenever a link is saved via a signal.
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bgneal@202
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15 """
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bgneal@202
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16 if kwargs['created']:
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bgneal@202
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17 # we only have to update the parent category
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bgneal@202
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18 link = kwargs['instance']
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bgneal@202
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19 cat = link.category
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bgneal@202
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20 cat.count = Link.public_objects.filter(category=cat).count()
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bgneal@202
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21 cat.save()
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bgneal@202
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22 else:
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bgneal@202
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23 # update all categories just to be safe (an existing link could
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bgneal@202
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24 # have been moved from one category to another
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bgneal@202
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25 cats = Category.objects.all()
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bgneal@202
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26 for cat in cats:
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bgneal@202
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27 cat.count = Link.public_objects.filter(category=cat).count()
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bgneal@202
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28 cat.save()
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bgneal@202
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29
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bgneal@202
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30
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bgneal@202
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31 def on_link_delete(sender, **kwargs):
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bgneal@202
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32 """This function updates the count field for the link's parent
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bgneal@202
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33 category. It is called when a link is deleted via a signal.
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bgneal@202
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34 """
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bgneal@202
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35 # update the parent category
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bgneal@202
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36 link = kwargs['instance']
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bgneal@202
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37 cat = link.category
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bgneal@202
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38 cat.count = Link.public_objects.filter(category=cat).count()
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bgneal@202
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39 cat.save()
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bgneal@202
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40
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bgneal@202
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41
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bgneal@921
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42 post_save.connect(on_link_save, sender=Link, dispatch_uid='weblinks.receivers')
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bgneal@921
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43 post_delete.connect(on_link_delete, sender=Link, dispatch_uid='weblinks.receivers')
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