I've created a graphql-codegen plugin that generates type-safe hooks for GraphQL queries for Flutter!
Tags: flutter, graphql
Published: 2022-01-01 04:24:57

---
title: I've created a graphql-codegen plugin that generates type-safe hooks for GraphQL queries for Flutter!
published: true
description: 
tags: flutter, graphql
//cover_image: https://direct_url_to_image.jpg
---

If you are a Flutter & GraphQL fan, please try it.
(And if you like it, please give it a star ⭐️)
https://github.com/kazuyaseki/graphql-codegen-flutter-artemis-hooks

## Motivation
I'm from React, and when building an application with React + Apollo configuration, I really liked the experience of using graphql-codegen to generate hooks like this

```tsx
export function useFetchUserQuery(baseOptions?: ApolloReactHooks.QueryHookOptions<FetchUserQuery, FetchUserQueryVariables>) {
    return ApolloReactHooks.useQuery<FetchUserQuery, FetchUserQueryVariables>(FetchUserDocument, baseOptions);
}
```
(This is the code that will be generated when you use this plugin with `withHooks` set to true.)
https://www.graphql-code-generator.com/plugins/typescript-react-apollo

I want to develop with the same experience in Flutter! So I created this plugin.
https://github.com/kazuyaseki/graphql-codegen-flutter-artemis-hooks

In Flutter, there is a library called [artemis](https://pub.dev/packages/artemis) that generates the type definitions, so this plugin is based on that.

For example, suppose you define a query like this as a .graphql file

```graphql
query ExampleQuery {
  objects {
    id
    name
  }
}

mutation TestMutation($variable: String!) {
  testMutation(variable: $variable) {
    result
  }
}
```

This plugin will generate the following hooks function


```dart
import 'package:flutter/material.dart';
import 'package:flutter_hooks/flutter_hooks.dart';
import 'package:graphql_flutter/graphql_flutter.dart';
import 'package:gql/ast.dart';
import 'package:your_project/your_artemis_generated/graphql_api.dart';

QueryResult useQuery<DataType>(BuildContext context, DocumentNode query,
    [Map<String, dynamic>? variables]) {
  final client = GraphQLProvider.of(context).value;
  final state =
      useState<QueryResult>(QueryResult(source: QueryResultSource.network));

  useEffect(() {
    late Future<QueryResult> promise;

    if (variables ! = null) {
      promise = client.query(
        QueryOptions(document: query, variables: variables),
      );
    } else {
      promise = client.query(
        QueryOptions(document: query),
      );
    }
    promise.then((result) {
      state.value = result;
    });

    return () {};
  }, []);
  return state.value;
}

class ExampleQuery$QueryReturnType {
  bool isLoading;
  OperationException? exception;
  ExampleQuery$Query? data;

  ExampleQuery$QueryReturnType(this.isLoading, this.exception, this.data);
}

ExampleQuery$QueryReturnType useExampleQueryQuery<DataType>(BuildContext context) {
  final result = useQuery<ExampleQuery$Query>(context, EXAMPLE_QUERY_QUERY_DOCUMENT);
  return ExampleQuery$QueryReturnType(result.isLoading, result.exception, result.data == null ? null : ExampleQuery$Query.fromJson(result.data!));
}

class TestMutation$MutationReturnType {
  bool isLoading;
  OperationException? exception;
  TestMutation$Mutation? data;

  TestMutation$MutationReturnType(this.isLoading, this.exception, this.data);
}

TestMutation$MutationReturnType useTestMutationQuery<DataType>(BuildContext context, TestMutationArguments variables) {
  final result = useQuery<TestMutation$Mutation>(context, TEST_MUTATION_MUTATION_DOCUMENT, variables.toJson());
  return TestMutation$MutationReturnType(result.isLoading, result.exception, result.data == null ? null : TestMutation$Mutation.fromJson(result.data!));
}
```

Then all that's left to do is import the above file and use the hooks! 🔥

```dart
class PageWidget extends HookWidget {
  const PageWidget({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    final queryResult = useExampleQueryQuery(context);
    final mutationResult = useTestMutationQuery(context, TestMutationArguments(variable: ""));

    return ...
  }
}
```

## Usage

### Installation

```bash
npm i --save-dev graphql-codegen-flutter-artemis-hooks
```

### Create a configuration file for graphql-codegen.

Create a configuration file for graphql-codegen, including the schema, the path to the .graphql file, and the path to the artemis-generated file.

```yml:codegen.yml
schema: your_schema_file.graphql
documents: '. /your_project/**/*.graphql'.
generates:
  your_project/generated_hooks.dart:
    config:
      artemisImportPath: package:your_project/your_artemis_generated/graphql_api.dart
    plugins:
      - graphql-codegen-flutter-artemis-hooks
```

### Run graphql-codegen

If you do not have graphql-codegen itself installed, install the following `@graphql-codegen/cli`.

```bash
npm i --save-dev @graphql-codegen/cli
```

Then add the following script to package.json and run `npm run codegen`!

```json
{
  "scripts": {
    "codegen": "graphql-codegen"
  },
}
```
That's it, I hope you find it useful!