Build GraphQL Requests with Convertors

Convertor Replaces Strategy Registration

The Convertor pattern replaces the old strategy registration approach. There is no longer a need to register requests - Convertors compose directly.

Build GraphQL Requests with Convertors

Overview

In the Convertor pattern, GraphQL requests are built by Convertor functions that transform typed parameters into Ferry operation requests. There is no registration step - Convertors are composed directly in @riverpod providers.

Request Convertors

List Query Request

@riverpod
Convertor<GQueryAttendeeReq, ListRequestParams<GattendeeFilters, GattendeeOrder>>
attendeeListQueryConvertor(Ref ref) {
  return Convertor((params) {
    return GQueryAttendeeReq((builder) {
      builder
        ..requestId = 'attendee_list_${params.toString()}'
        ..vars.G_filter = params.filter?.toBuilder()
        ..vars.G_sort = params.sort?.toBuilder()
        ..vars.G_skip = params.skip
        ..vars.G_take = params.take;
    });
  });
}

Single Item Query Request

@riverpod
Convertor<GQueryAttendeeReq, SingleRequestParams<GattendeeFilters>>
attendeeItemQueryConvertor(Ref ref) {
  return Convertor((params) {
    return GQueryAttendeeReq((builder) {
      builder
        ..requestId = 'attendee_item_${params.toString()}'
        ..vars.G_filter = params.filter?.toBuilder()
        ..vars.G_take = 1;
    });
  });
}

Mutation Request

@riverpod
Convertor<GMutateAttendeeSaveReq, (UpsertRequestParams<GMutateAttendeeSaveVars>, bool)>
attendeeUpsertConvertor(Ref ref) {
  return Convertor((params) {
    return GMutateAttendeeSaveReq((builder) {
      builder
        ..requestId = 'attendee_upsert_${params.$1.toString()}'
        ..vars = params.$1.vars.toBuilder();
      if (params.$2) {
        builder..optimisticResponse.attendeeSave.id = '__optimistic__';
      }
    });
  });
}

Subscription Request

@riverpod
Convertor<GSubscribeToMessagesReq, SubscriptionRequestParams<ChatContext>>
messageSubscriptionConvertor(Ref ref) {
  return Convertor((params) {
    return GSubscribeToMessagesReq((builder) {
      builder
        ..requestId = 'message_subscription'
        ..updateCacheHandlerContext = params.context?.toJson();
    });
  });
}

Composing into Datasource Pipelines

Request Convertors are fed into GraphQLRequestExecutor:

@riverpod
StreamConvertor<List<GQueryAttendeeData_attendee_items>,
    ListRequestParams<GattendeeFilters, GattendeeOrder>>
attendeeListDatasource(Ref ref) {
  return GraphQLRequestExecutor<GQueryAttendeeData,
        ListRequestParams<GattendeeFilters, GattendeeOrder>, GQueryAttendeeVars>(
      gqlClient: ref.watch(gqlClientProvider),
      convertor: ref.watch(attendeeListQueryConvertorProvider),
    )
    .then(GraphQLStreamConvertor())
    .map((data) => data.attendee!.items!.nonNulls.toList());
}

Migration from Strategy Registration

Before (Strategy)	After (Convertor)
context.registerStrategy(ChatListRequestStrategy())	ref.watch(chatListQueryConvertorProvider)
Strategy key enum	Not needed
DatasourceModule	Not needed
RequestContext	Not needed