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An implementation of GraphQL's type system in Dart. Basis of graphql_server2.

GraphQL Schema 2 #

Pub Version (including pre-releases) Null Safety Gitter License melos

An implementation of GraphQL's type system in Dart. Supports any platform where Dart runs. The decisions made in the design of this library were done to make the experience as similar to the JavaScript reference implementation as possible, and to also correctly implement the official specification.

Contains functionality to build all GraphQL types:

  • String
  • Int
  • Float
  • Boolean
  • GraphQLObjectType
  • GraphQLUnionType
  • GraphQLEnumType
  • GraphQLInputObjectType
  • Date - ISO-8601 Date string, deserializes to a Dart DateTime object

Of course, for a full description of GraphQL's type system, see the official GraphQL Specification. Mostly analogous to graphql-js; many names are verbatim.

Usage #

It's easy to define a schema with the helper functions:

final GraphQLSchema todoSchema = GraphQLSchema(
    query: objectType('Todo', [
  field('text', graphQLString.nonNullable()),
  field('created_at', graphQLDate)

All GraphQL types are generic, in order to leverage Dart's strong typing support.

Serialization #

GraphQL types can serialize and deserialize input data. The exact implementation of this depends on the type.

var iso8601String = graphQLDate.serialize(;
var date = graphQLDate.deserialize(iso8601String);

Validation #

GraphQL types can validate input data.

var validation = myType.validate('@root', {...});

if (validation.successful) {
} else {

Helpers #

  • graphQLSchema - Create a GraphQLSchema
  • objectType - Create a GraphQLObjectType with fields
  • field - Create a GraphQLField with a type/argument/resolver
  • listOf - Create a GraphQLListType with the provided innerType
  • inputObjectType - Creates a GraphQLInputObjectType
  • inputField - Creates a field for a GraphQLInputObjectType

Types #

All of the GraphQL scalar types are built in, as well as a Date type:

  • graphQLString
  • graphQLId
  • graphQLBoolean
  • graphQLInt
  • graphQLFloat
  • graphQLDate

Non-Nullable Types #

You can easily make a type non-nullable by calling its nonNullable method.

List Types #

Support for list types is also included. Use the listType helper for convenience.

/// A non-nullable list of non-nullable integers

Input values and parameters #

Take the following GraphQL query:

   anime {
     characters(title: "Hunter x Hunter") {

And subsequently, its schema:

type AnimeQuery {
  characters($title: String!): [Character!]

type Character {
  name: String
  age: Int

The field characters accepts a parameter, title. To reproduce this in package:graphql_schema2, use GraphQLFieldInput:

final GraphQLObjectType queryType = objectType('AnimeQuery', fields: [
    inputs: [
      new GraphQLFieldInput('title', graphQLString.nonNullable())

final GraphQLObjectType characterType = objectType('Character', fields: [
  field('name', graphQLString),
  field('age', graphQLInt),

In the majority of cases where you use GraphQL, you will be delegate the actual fetching of data to a database object, or some asynchronous resolver function.

package:graphql_schema2 includes this functionality in the resolve property, which is passed a context object and a Map<String, dynamic> of arguments.

A hypothetical example of the above might be:

var field = field(
  resolve: (_, args) async {
    return await myDatabase.findCharacters(args['title']);
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An implementation of GraphQL's type system in Dart. Basis of graphql_server2.

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