Graphql

Introduction

This is a query language for your API.

Example

A example Query and Response provides an example. It is used by

• Facebook
• PsyPal
• Twitter
• Github

Core Concepts

Data Types

• Int signed 32-bit integer
• Float signed double-precision floating-point value
• String utf8 character sequence
• Boolean true or false values
• ID Unique identifier, Used to re-fetch an object or a the key for a cache

Structure Types

type Author {
  id: ID,
  firstName: String
  lastName: String
  rating: Float
  numOfCourses: Int
}

Enums

enum language {
  ENGLISH
  SPANISH
  FRENCH
}

Query and Mutation Types

Every GraphQL service has a query type. It may or may not have a mutation type. Tyey act as an entry point into the schema.

schema {
  query: Query
  mutation: Mutation
}

Examples

type Query {
   author_details: [Author]
}

type Mutation {
   addAuthor: [firstName: String, lastName: String_):Author
}

Allowing Null values

Adding a bang to the fields means the field is allowed to be nullable.

type Author {
  id: ID!,
  firstName: String
  lastName: String
  rating: Float
  numOfCourses: Int
}

Queries

Arguments

Creating queries is straight forward

{
    viewer {
        login
        bio
        id
        name
        followers (last : 3) {
           nodes {
              id,
              bio
           }
        } 
    }
}

Alias

To prevent duplicate returned data names you need to add aliases.

{
    viewer {
        login
        bio
        id
        name
        firstfollowers: followers (first : 3) {
           nodes {
              id,
              bio
           }
        }
        lastfollowers: followers (last : 3) {
           nodes {
              id,
              bio
           }
        } 
    }
}

Fragments

To make query less duplicated you can write macros and use the eclipse.

{
    viewer {
        login
        bio
        id
        name
        firstfollowers: followers (first : 3) {
           nodes {
              ...userInfo
           }
        }
        lastfollowers: followers (last : 3) {
           nodes {
              ...userInfo
           }
        } 
    }
}

fragment userInfo on User {
    id
    bio
    bioHTML