diff options
Diffstat (limited to 'tagging/fields.py')
-rw-r--r-- | tagging/fields.py | 107 |
1 files changed, 107 insertions, 0 deletions
diff --git a/tagging/fields.py b/tagging/fields.py new file mode 100644 index 0000000..f52daff --- /dev/null +++ b/tagging/fields.py @@ -0,0 +1,107 @@ +""" +A custom Model Field for tagging. +""" +from django.db.models import signals +from django.db.models.fields import CharField +from django.utils.translation import ugettext_lazy as _ + +from tagging import settings +from tagging.models import Tag +from tagging.utils import edit_string_for_tags + +class TagField(CharField): + """ + A "special" character field that actually works as a relationship to tags + "under the hood". This exposes a space-separated string of tags, but does + the splitting/reordering/etc. under the hood. + """ + def __init__(self, *args, **kwargs): + kwargs['max_length'] = kwargs.get('max_length', 255) + kwargs['blank'] = kwargs.get('blank', True) + super(TagField, self).__init__(*args, **kwargs) + + def contribute_to_class(self, cls, name): + super(TagField, self).contribute_to_class(cls, name) + + # Make this object the descriptor for field access. + setattr(cls, self.name, self) + + # Save tags back to the database post-save + signals.post_save.connect(self._save, cls, True) + + def __get__(self, instance, owner=None): + """ + Tag getter. Returns an instance's tags if accessed on an instance, and + all of a model's tags if called on a class. That is, this model:: + + class Link(models.Model): + ... + tags = TagField() + + Lets you do both of these:: + + >>> l = Link.objects.get(...) + >>> l.tags + 'tag1 tag2 tag3' + + >>> Link.tags + 'tag1 tag2 tag3 tag4' + + """ + # Handle access on the model (i.e. Link.tags) + if instance is None: + return edit_string_for_tags(Tag.objects.usage_for_model(owner)) + + tags = self._get_instance_tag_cache(instance) + if tags is None: + if instance.pk is None: + self._set_instance_tag_cache(instance, '') + else: + self._set_instance_tag_cache( + instance, edit_string_for_tags(Tag.objects.get_for_object(instance))) + return self._get_instance_tag_cache(instance) + + def __set__(self, instance, value): + """ + Set an object's tags. + """ + if instance is None: + raise AttributeError(_('%s can only be set on instances.') % self.name) + if settings.FORCE_LOWERCASE_TAGS and value is not None: + value = value.lower() + self._set_instance_tag_cache(instance, value) + + def _save(self, **kwargs): #signal, sender, instance): + """ + Save tags back to the database + """ + tags = self._get_instance_tag_cache(kwargs['instance']) + if tags is not None: + Tag.objects.update_tags(kwargs['instance'], tags) + + def __delete__(self, instance): + """ + Clear all of an object's tags. + """ + self._set_instance_tag_cache(instance, '') + + def _get_instance_tag_cache(self, instance): + """ + Helper: get an instance's tag cache. + """ + return getattr(instance, '_%s_cache' % self.attname, None) + + def _set_instance_tag_cache(self, instance, tags): + """ + Helper: set an instance's tag cache. + """ + setattr(instance, '_%s_cache' % self.attname, tags) + + def get_internal_type(self): + return 'CharField' + + def formfield(self, **kwargs): + from tagging import forms + defaults = {'form_class': forms.TagField} + defaults.update(kwargs) + return super(TagField, self).formfield(**defaults) |