GraphQL Query Hook

useQuery.dart

import 'package:flutter/widgets.dart';
import 'package:flutter_hooks/flutter_hooks.dart';
import 'package:graphql/internal.dart';
import 'package:graphql/client.dart';

QueryResult useQuery(
    {@required GraphQLClient client, @required QueryOptions options}) {
  return Hook.use(_QueryHook(client: client, options: options));
}

class _QueryHook extends Hook<QueryResult> {
  final QueryOptions options;
  final GraphQLClient client;

  _QueryHook({@required this.options, @required this.client});

  @override
  _QueryHookState createState() => _QueryHookState();
}

class _QueryHookState<T> extends HookState<QueryResult, _QueryHook> {
  ObservableQuery observableQuery;

  WatchQueryOptions get _options {
    FetchPolicy fetchPolicy = hook.options.fetchPolicy;

    if (fetchPolicy == FetchPolicy.cacheFirst) {
      fetchPolicy = FetchPolicy.cacheAndNetwork;
    }

    return WatchQueryOptions(
      document: hook.options.document,
      variables: hook.options.variables,
      fetchPolicy: fetchPolicy,
      errorPolicy: hook.options.errorPolicy,
      pollInterval: hook.options.pollInterval,
      fetchResults: true,
      context: hook.options.context,
      optimisticResult: hook.options.optimisticResult,
    );
  }

  void _initQuery() {
    observableQuery?.close();
    observableQuery = hook.client.watchQuery(_options);
  }

  @override
  void initHook() {
    super.initHook();
    _initQuery();
  }

  @override
  void didUpdateHook(_QueryHook oldWidget) {
    super.didUpdateHook(oldWidget);

    if (!observableQuery.options.areEqualTo(_options)) {
      _initQuery();
    }
  }

  @override
  void dispose() {
    observableQuery?.close();
    super.dispose();
  }

  @override
  QueryResult build(BuildContext context) {
    return useStream<QueryResult>(
      observableQuery.stream,
      initialData: QueryResult(
        loading: true,
      ),
    ).data;
  }
}