newtagging/managers.py

   1 """
   2 Custom managers for Django models registered with the tagging
   3 application.
   4 """
   5 from django.contrib.contenttypes.models import ContentType
   6 from django.db import models
   7
   8
   9 class ModelTagManager(models.Manager):
  10     """
  11     A manager for retrieving tags for a particular model.
  12     """
  13     def __init__(self, tag_model):
  14         super(ModelTagManager, self).__init__()
  15         self.tag_model = tag_model
  16
  17     def get_query_set(self):
  18         content_type = ContentType.objects.get_for_model(self.model)
  19         return self.tag_model.objects.filter(
  20             items__content_type__pk=content_type.pk).distinct()
  21
  22     def related(self, tags, *args, **kwargs):
  23         return self.tag_model.objects.related_for_model(tags, self.model, *args, **kwargs)
  24
  25     def usage(self, *args, **kwargs):
  26         return self.tag_model.objects.usage_for_model(self.model, *args, **kwargs)
  27
  28
  29 class ModelTaggedItemManager(models.Manager):
  30     """
  31     A manager for retrieving model instances based on their tags.
  32     """
  33     def __init__(self, tag_model):
  34         super(ModelTaggedItemManager, self).__init__()
  35         self.intermediary_table_model = tag_model.objects.intermediary_table_model
  36
  37     def related_to(self, obj, queryset=None, num=None):
  38         if queryset is None:
  39             return self.intermediary_table_model.objects.get_related(obj, self.model, num=num)
  40         else:
  41             return self.intermediary_table_model.objects.get_related(obj, queryset, num=num)
  42
  43     def with_all(self, tags, queryset=None):
  44         if queryset is None:
  45             return self.intermediary_table_model.objects.get_by_model(self.model, tags)
  46         else:
  47             return self.intermediary_table_model.objects.get_by_model(queryset, tags)
  48
  49     def with_any(self, tags, queryset=None):
  50         if queryset is None:
  51             return self.intermediary_table_model.objects.get_union_by_model(self.model, tags)
  52         else:
  53             return self.intermediary_table_model.objects.get_union_by_model(queryset, tags)
  54
  55
  56 class TagDescriptor(object):
  57     """
  58     A descriptor which provides access to a ``ModelTagManager`` for
  59     model classes and simple retrieval, updating and deletion of tags
  60     for model instances.
  61     """
  62     def __init__(self, tag_model):
  63         self.tag_model = tag_model
  64
  65     def __get__(self, instance, owner):
  66         if not instance:
  67             tag_manager = ModelTagManager(self.tag_model)
  68             tag_manager.model = owner
  69             return tag_manager
  70         else:
  71             return self.tag_model.objects.get_for_object(instance)
  72
  73     def __set__(self, instance, value):
  74         self.tag_model.objects.update_tags(instance, value)
  75
  76     def __del__(self, instance):
  77         self.tag_model.objects.update_tags(instance, [])
  78