managers.py 文件源码

def _validate_field_name(self):
        field_names = self.model._meta.get_all_field_names()

        # If a custom name is provided, make sure the field exists on the model
        if self.__field_name is not None and self.__field_name not in field_names:
            raise ValueError("%s couldn't find a field named %s in %s." % \
                (self.__class__.__name__, self.__field_name, self.model._meta.object_name))

        # Otherwise, see if there is a field called either 'site' or 'sites'
        else:
            for potential_name in ['site', 'sites']:
                if potential_name in field_names:
                    self.__field_name = potential_name
                    self.__is_validated = True
                    break

        # Now do a type check on the field (FK or M2M only)
        try:
            field = self.model._meta.get_field(self.__field_name)
            if not isinstance(field, (models.ForeignKey, models.ManyToManyField)):
                raise TypeError("%s must be a ForeignKey or ManyToManyField." %self.__field_name)
        except FieldDoesNotExist:
            raise ValueError("%s couldn't find a field named %s in %s." % \
                    (self.__class__.__name__, self.__field_name, self.model._meta.object_name))
        self.__is_validated = True