Implement Optimistic Updates

Convertor Tuple Input Pattern

Mutations use a (Params, bool) tuple to optionally enable optimistic responses.

Implement Optimistic Updates

Mutation Request Convertor with Tuple Input

@riverpod
Convertor<GMutateAttendeeSaveReq, (UpsertRequestParams<GMutateAttendeeSaveVars>, bool)>
attendeeUpsertConvertor(Ref ref) {
  return Convertor((params) {
    final (requestParams, optimistic) = params;
    return GMutateAttendeeSaveReq((builder) {
      builder
        ..requestId = 'attendee_upsert_${requestParams.toString()}'
        ..vars = requestParams.vars.toBuilder();
      if (optimistic) {
        builder
          ..optimisticResponse.attendeeSave.id = '__optimistic__'
          ..optimisticResponse.attendeeSave.fullName =
              requestParams.vars.attendeeArg?.fullName;
      }
    });
  });
}

Repository Method

Stream<AttendeeModel> upsert({
  required AttendeeUpsertInput input,
  bool optimistic = true,
}) {
  final vars = inputConvertor.execute(input);
  return upsertDatasource
      .thenMap(mutationModelConvertor)
      .execute((UpsertRequestParams(vars: vars), optimistic));
}

How It Works

1. Optimistic = true: Ferry immediately updates cache with optimistic data
2. Server responds: Ferry replaces optimistic entry with real data
3. Error case: Ferry rolls back the optimistic update automatically