GraphQL/graphql.pdf.txt

graphql

#graphql

Table of Contents

About

Chapter 1: Getting started with graphql

Remarks

When should I use GraphQL?

Implementations

Client Libraries

Dev Tools

Versions

Examples

Server Installation & Implementation

GraphQL.js

Example Server

Server Middleware Alternatives

GraphQL Query Language (GQL)

Query for All Film Titles from Star Wars Schema

Query for Planet Residents to Star Wars film "A New Hope"

Schema Definition

Schema Object Type

Schema Query

Query Nick's Friend's Friend's Friends

Credits

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About

You can share this PDF with anyone you feel could benefit from it, downloaded the latest version 
from: graphql

It is an unofficial and free graphql ebook created for educational purposes. All the content is 
extracted from Stack Overflow Documentation, which is written by many hardworking individuals at 
Stack Overflow. It is neither affiliated with Stack Overflow nor official graphql.

The content is released under Creative Commons BY-SA, and the list of contributors to each 
chapter are provided in the credits section at the end of this book. Images may be copyright of 
their respective owners unless otherwise specified. All trademarks and registered trademarks are 
the property of their respective company owners.

Use the content presented in this book at your own risk; it is not guaranteed to be correct nor 
accurate, please send your feedback and corrections to info@zzzprojects.com

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Chapter 1: Getting started with graphql

Remarks

GraphQL is a query language for APIs and a runtime for fulfilling those queries with 
your existing data. GraphQL provides a complete and understandable description of 
the data in your API, gives clients the power to ask for exactly what they need and 
nothing more, makes it easier to evolve APIs over time, and enables powerful 
developer tools.

When should I use GraphQL?

GraphQL is intended to be the outward facing HTTP API for any kind of application but it is most 
powerful when the data is normalized with highly interconnected Collections|Tables|Nodes. The 
GraphQL Query Language (GQL) is designed to project interconnected data in a very intuitive and 
flexible way.

Implementations

GraphQL itself is a Spec and is implemented by a number of different programming languages. 
These are the most popular supported languages

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GraphQL.js
graphql-ruby
Graphene (Python)
Sangria (Scala)
graphql-java
graphql-clj (Clojure)
graphql-go
graphql-php
graphql-dotnet (C# / .Net)
absinthe (Elixir)

Client Libraries

Running queries from the client side can be done with any HTTP client but client side libraries can 
be very beneficial.

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Relay
Apollo
Lokka

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Dev Tools

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graphiql /ˈɡrafək(ə)l/ - An interactive in-browser GraphQL IDE.
libgraphqlparser - A GraphQL query language parser in C++ with C and C++ APIs.
GraphQL Language Service - An interface for building GraphQL language services for IDEs 
(diagnostics, autocomplete etc).

Versions

Version Release Date

v0.5.0

2016-04-08

v0.6.0

2016-05-10

v0.6.1

2016-07-07

v0.6.2

2016-07-21

v0.7.0

2016-08-26

v0.7.1

2016-09-29

v0.7.2

2016-10-10

v0.8.0

2016-11-10

v0.8.1

2016-11-11

v0.8.2

2016-11-16

Examples

Server Installation & Implementation

GraphQL.js

GraphQL.js is a JavaScript reference implementation for GraphQL. You can install it via npm:

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Initialize npm in your project if you have not done so already: npm init
Install GraphQL.js from npm: npm install --save graphql

Example Server

var { graphql, buildSchema } = require('graphql'); 

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// Construct a schema, using GraphQL schema language 
var schema = buildSchema(` 
  type Query { 
    hello: String 
  } 
`); 

// The root provides a resolver function for each API endpoint 
var root = { 
  hello: () => { 
    return 'Hello world!'; 
  }, 
}; 

// Run the GraphQL query '{ hello }' and print out the response 
graphql(schema, '{ hello }', root).then((response) => { 
  console.log(response); 
});

Server Middleware Alternatives

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Express GraphQL Middleware
Hapi GraphQL Middleware
Koa GraphQL Middleware

GraphQL Query Language (GQL)

Instead of defining URL endpoints for each data resource, in GraphQL you define a single 
endpoint that accepts GraphQL queries. Unlike traditional database query languages, GraphQL 
Query Language (GQL) is a projection of data returned by a root level query. The GraphQL 
schema will define the data model and root level queries and mutations. GQL executes those 
queries and defines what data to return.

Query for All Film Titles from Star Wars Schema

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GraphiQL Query

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Query for Planet Residents to Star Wars film "A New Hope"

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GraphiQL Query

Notice how the root query film() takes in the id parameter of the film "A New Hope" and the 
projection from GQL returns the title, planets connected to the film, and then resident names of the 
planets. Check out the Star Wars GraphiQL site to experiment with querying in GraphQL.

Schema Definition

In GraphQL the Schema defines the root execution queries and mutations as well as the types for 
your data.

Schema Object Type

The Person type has two fields, one is a standard Scalar type and the other represents a 
relationship to a list of other Person types that are 'friends'. Linking other types is what makes 
GraphQL so powerful. Now in GraphQL Query Language (GQL), the client can traverse the friends 
graph without any additional code or advanced querying.

type Person { 
  id: ID 
  name: String 
  friends: [Person] 
}

Schema Query

The person query looks up a single person by it's id. This is the entry point to your data for clients 
using GQL.

type Query { 
  person(id: ID!): Person 
}

Query Nick's Friend's Friend's Friends

Now that we have a Person type and a person root query we can look up a person and as many 
degrees of separation we want of the person's friends network.

query { 
  person(id: 'nick'){ 
    id 
    name 
    friends{ 
      id 
      name 
      friends{ 
        id 
        name 
        friends{ 

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          id 
          name 
        } 
      } 
    } 
  } 
}

Read Getting started with graphql online: https://riptutorial.com/graphql/topic/7649/getting-started-
with-graphql

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Credits

S. 
No

1

Chapters

Contributors

Getting started with 
graphql

Community, jengeb, Nikordaris

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