base.py 文件源码

def _prepare(cls):
        """
        Creates some methods once self._meta has been populated.
        """
        opts = cls._meta
        opts._prepare(cls)

        if opts.order_with_respect_to:
            cls.get_next_in_order = curry(cls._get_next_or_previous_in_order, is_next=True)
            cls.get_previous_in_order = curry(cls._get_next_or_previous_in_order, is_next=False)

            # Defer creating accessors on the foreign class until it has been
            # created and registered. If remote_field is None, we're ordering
            # with respect to a GenericForeignKey and don't know what the
            # foreign class is - we'll add those accessors later in
            # contribute_to_class().
            if opts.order_with_respect_to.remote_field:
                wrt = opts.order_with_respect_to
                remote = wrt.remote_field.model
                lazy_related_operation(make_foreign_order_accessors, cls, remote)

        # Give the class a docstring -- its definition.
        if cls.__doc__ is None:
            cls.__doc__ = "%s(%s)" % (cls.__name__, ", ".join(f.name for f in opts.fields))

        get_absolute_url_override = settings.ABSOLUTE_URL_OVERRIDES.get(opts.label_lower)
        if get_absolute_url_override:
            setattr(cls, 'get_absolute_url', get_absolute_url_override)

        if not opts.managers or cls._requires_legacy_default_manager():
            if any(f.name == 'objects' for f in opts.fields):
                raise ValueError(
                    "Model %s must specify a custom Manager, because it has a "
                    "field named 'objects'." % cls.__name__
                )
            manager = Manager()
            manager.auto_created = True
            cls.add_to_class('objects', manager)

        signals.class_prepared.send(sender=cls)