serializer field의 값을 가져오는 도중 ObjectDoesNotExist에러 발생하면 그냥 None을 반환한다.

e.g. code = serializers.CharField(source='notification.event_type.code')에서 notification이 event_type 외래키로 참조하는 CommunicationEventType 인스턴스가 존재하지 않으면 .data[’code’]는 None이다.

serializer field get_attribute()

[rest_framework/fields.py]

def get_attribute(instance, attrs):
    """
    Similar to Python's built in `getattr(instance, attr)`,
    but takes a list of nested attributes, instead of a single attribute.

    Also accepts either attribute lookup on objects or dictionary lookups.
    """
    for attr in attrs:
        try:
            if isinstance(instance, Mapping):
                instance = instance[attr]
            else:
                instance = getattr(instance, attr)
        except ObjectDoesNotExist:
            return None
        if is_simple_callable(instance):
            try:
                instance = instance()
            except (AttributeError, KeyError) as exc:
                # If we raised an Attribute or KeyError here it'd get treated
                # as an omitted field in `Field.get_attribute()`. Instead we
                # raise a ValueError to ensure the exception is not masked.
                raise ValueError('Exception raised in callable attribute "{}"; original exception was: {}'.format(attr, exc))

    return instance