Question

class BaseCommentAbstractModel(models.Model):
    """
    An abstract base class that any custom comment models probably should
    subclass.
    """

    # Content-object field
    content_type   = models.ForeignKey(ContentType,
            verbose_name=_('content type'),
            related_name="content_type_set_for_%(class)s")
    object_pk      = models.TextField(_('object ID'))
    content_object = generic.GenericForeignKey(ct_field="content_type", fk_field="object_pk")

    # Metadata about the comment
    site        = models.ForeignKey(Site)

    class Meta:
        abstract = True

    def get_content_object_url(self):
        """
        Get a URL suitable for redirecting to the content object.
        """
        return urlresolvers.reverse(
            "comments-url-redirect",
            args=(self.content_type_id, self.object_pk)
        )

I have two questions related to this model code.

1. models.TextField(_('object ID')) Object ID which probably is the verbose Name of this TextField ,How does it reflect in the database?
2. Why do Django relies on field abstract of Meta innerclass instead of using abc(AbstractBaseClass) module?

Answer 1

1. That is indeed that verbose name. I assume you understand that _ is the call to ugettext_lazy which is for localizing strings. This is the verbose name of the field. The verbose name is not represented in the database. The name of the field in the database would be object_pk.

2. I’m not a django dev so I can’t speak with authority, but some things are obvious. ABC is new in Python 2.6. This is an issue because as of the most recent release the minimum python version was finally moved to 2.5. This has been being bumped quite quickly as of late. For example it was only on django 1.2 that python 2.4 became required. Abstract models have existed at least as far back as django 1.0 and I think even further back then that (though I can’t recall for sure) So even if ABC would be suitable (which I’m not sure it is since the behavior of models is kinda complex), it wouldn’t be suitable for django at this point due to the required python version.

Additionally there is some complexity in managing classes that represent the database rather than just data structures. I’m not sure how much this impacts abstract models but for example you can’t perform field hiding on django attributes that are Field instances.