GraphQL

This quick reference cheat sheet provides a brief overview of GraphQL.

#Getting started

#Overview

  • An alternative approach to RESTful APIs
  • GraphQL is a query language for APIs
  • Easily describe the shape of the GraphQL API using clear shared terms.
  • Clients issue queries/mutations to read and update data
  • GraphQL syntax can express complex entity relations
  • Libraries to implement GraphQL in different languages

#Schema

schema GraphQL schema definition
query Read and traverse data
mutation Modify data or trigger an action
subscription Run a query when an event occurs

#Built-in Scalar Types

Int Signed 32‐bit integer
Float Signed double-precision floating-point value
String UTF‐8 character sequence
Boolean true or false
ID A Unique identifier

#Type Definitions

scalar Scalar Type
type Object Type
interface Interface Type
union Union Type
enum Enum Type
input Input Object Type

#Type Modifiers

String Nullable String
String! Non-null String
[String] List of nullable Strings
[String]! Non-null list of nullable Strings
[String!]! Non-null list of non-null Strings

#Input Arguments

#Basic Input

type Query {
    users(limit: Int): [User]
}

#Input with default value

type Query {
    users(limit: Int = 10): [User]
}

#Input with multiple arguments

type Query {
    users(limit: Int, sort: String): [User]
}

#Input with multiple arguments and default values

type Query {
    users(limit: Int = 10, sort: String): [User]
}
type Query {
    users(limit: Int, sort: String = "asc"): [User]
}
type Query {
    users(limit: Int = 10, sort: String = "asc"): [User]
}

#Input Types

input ListUsersInput {
    limit: Int
    since_id: ID
}
type Mutation {
    users(params: ListUsersInput): [User]!
}

#Custom Scalars

scalar Url
type User {
    name: String
    homepage: Url
}

#Interfaces

interface Foo {
    is_foo: Boolean
}
interface Goo {
    is_goo: Boolean
}
type Bar implements Foo {
    is_foo: Boolean
    is_bar: Boolean
}
type Baz implements Foo, Goo {
    is_foo: Boolean
    is_goo: Boolean
    is_baz: Boolean
}

Object implementing one or more Interfaces

#Unions

type Foo {
    name: String
}
type Bar {
    is_bar: String
}
union SingleUnion = Foo
union MultipleUnion = Foo | Bar
type Root {
    single: SingleUnion
    multiple: MultipleUnion
}

Union of one or more Objects

#Enums

enum USER_STATE {
    NOT_FOUND
    ACTIVE
    INACTIVE
    SUSPENDED
}
type Root {
    stateForUser(userID: ID!): USER_STATE!
    users(state: USER_STATE, limit: Int = 10): [User]
}

#Also see