graphql

GraphQL Client

Installation

First, depend on this package:

dependencies:
  graphql: ^3.0.0

And then import it inside your dart code:

import 'package:graphql/client.dart';

Migration Guide

Find the migration from version 2 to version 3 here.

Parsing at build-time

To parse documents at build-time use ast_builder from package:gql_code_gen:

dev_dependencies:
  gql_code_gen: ^0.1.0

Usage

To connect to a GraphQL Server, we first need to create a GraphQLClient. A GraphQLClient requires both a cache and a link to be initialized.

In our example below, we will be using the Github Public API. In our example below, we are going to use HttpLink which we will concatenate with AuthLink so as to attach our github access token. For the cache, we are going to use InMemoryCache.

// ...

final HttpLink _httpLink = HttpLink(
    uri: 'https://api.github.com/graphql',
);

final AuthLink _authLink = AuthLink(
    getToken: () async => 'Bearer $YOUR_PERSONAL_ACCESS_TOKEN',
);

final Link _link = _authLink.concat(_httpLink);

final GraphQLClient _client = GraphQLClient(
        cache: InMemoryCache(),
        link: _link,
    );

// ...

Combining Multiple Links

Using Concat

final Link _link = _authLink.concat(_httpLink);

Using Links.from

Link.from joins multiple links into a single link at once.

final Link _link = Link.from([_authLink, _httpLink]);

Once you have initialized a client, you can run queries and mutations.

Query

Creating a query is as simple as creating a multiline string:

const String readRepositories = r'''
  query ReadRepositories($nRepositories: Int!) {
    viewer {
      repositories(last: $nRepositories) {
        nodes {
          __typename
          id
          name
          viewerHasStarred
        }
      }
    }
  }
''';

Then create a QueryOptions object:

NB: for documentNode - Use our built-in help function - gql(query) to convert your document string to ASTs documentNode.

In our case, we need to pass nRepositories variable and the document name is readRepositories.

const int nRepositories = 50;

final QueryOptions options = QueryOptions(
    documentNode: gql(readRepositories),
    variables: <String, dynamic>{
        'nRepositories': nRepositories,
    },
);

And finally you can send the query to the server and await the response:

// ...

final QueryResult result = await _client.query(options);

if (result.hasException) {
    print(result.exception.toString());
}

final List<dynamic> repositories =
    result.data['viewer']['repositories']['nodes'] as List<dynamic>;

// ...

Mutations

Creating a Mutation is also similar to creating a query, with a small difference. First, start with a multiline string:

const String addStar = r'''
  mutation AddStar($starrableId: ID!) {
    action: addStar(input: {starrableId: $starrableId}) {
      starrable {
        viewerHasStarred
      }
    }
  }
''';

Then instead of the QueryOptions, for mutations we will MutationOptions, which is where we pass our mutation and id of the repository we are starring.

// ...

final MutationOptions options = MutationOptions(
  documentNode: gql(addStar),
  variables: <String, dynamic>{
    'starrableId': repositoryID,
  },
);

// ...

And finally you can send the query to the server and await the response:

// ...

final QueryResult result = await _client.mutate(options);

if (result.hasException) {
    print(result.exception.toString());
    return
}

final bool isStarred =
    result.data['action']['starrable']['viewerHasStarred'] as bool;

if (isStarred) {
  print('Thanks for your star!');
  return;
}

// ...

AST documents

We are deprecating document and recommend you update your application to use documentNode instead. document will be removed from the api in a future version.

For example:

// ...

final MutationOptions options = MutationOptions(
  documentNode: gql(addStar),
  variables: <String, dynamic>{
    'starrableId': repositoryID,
  },
);

// ...

With package:gql_code_gen you can parse your *.graphql files at build-time.

add_star.graphql:

mutation AddStar($starrableId: ID!) {
  action: addStar(input: {starrableId: $starrableId}) {
    starrable {
      viewerHasStarred
    }
  }
}

import 'package:gql/add_star.ast.g.dart' as add_star;

// ...

final MutationOptions options = MutationOptions(
  documentNode: add_star.document,
  variables: <String, dynamic>{
    'starrableId': repositoryID,
  },
);

// ...

Links

ErrorLink

Perform custom logic when a GraphQL or network error happens, such as logging or signing out.

final ErrorLink errorLink = ErrorLink(errorHandler: (ErrorResponse response) {
  Operation operation = response.operation;
  FetchResult result = response.fetchResult;
  OperationException exception = response.exception;
  print(exception.toString());
});