src/newtagging/managers.py

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