serializers.py 文件源码

def get_object(self, validated_data, instance=None):
        """
        Returns model object instance using the primary key values in the `validated_data`.
        If the instance is not found, depending on serializer's `allow_create` value, it will create a new model
        instance or raise an error.
        """
        pks = self.get_primary_keys(validated_data)
        checked_instance = None
        if pks:
            checked_instance = self.session.query(self.model).get(pks)
        else:
            checked_instance = instance

        if checked_instance is not None:
            return checked_instance

        if self.allow_create:
            return self.model()

        if self.allow_null:
            return checked_instance

        raise ValidationError('No instance of `{}` found with primary keys `{}`'.format(self.model.__name__, pks))