fields.py 文件源码

def _check_generic_foreign_key_existence(self):
        target = self.remote_field.model
        if isinstance(target, ModelBase):
            fields = target._meta.virtual_fields
            if any(isinstance(field, GenericForeignKey) and
                    field.ct_field == self.content_type_field_name and
                    field.fk_field == self.object_id_field_name
                    for field in fields):
                return []
            else:
                return [
                    checks.Error(
                        ("The GenericRelation defines a relation with the model "
                         "'%s.%s', but that model does not have a GenericForeignKey.") % (
                            target._meta.app_label, target._meta.object_name
                        ),
                        hint=None,
                        obj=self,
                        id='contenttypes.E004',
                    )
                ]
        else:
            return []