GraphQL 101

A gentle introduction to a different API paradigm

What is GraphQL?

Is a data query language created by Facebook for internal use and later released in 2015, It basically provides a new paradigm to exchange information with a server, it is an alternative to SOAP and REST APIs.

Main advantages of GraphQL

More simple data retrieval:

It allows you to customize your request and ask for as many or fewer fields you need in a simple call

Main advantages of GraphQL

Better performance:

It uses fewer round-trips to get the data you need

Main advantages of GraphQL

Strongly typed:

It uses an enforceable data schema which includes validations

Main advantages of GraphQL

It is a standard:

Defines a specific way to expose data and operations

Main advantages of GraphQL

Native discoverable:

Is self-documented and self-described which ease the introduction to users and developers

Who is using GraphQL?

Obviously their creators heavily use it:

 

https://developers.facebook.com/tools/explorer/

 

Who is using GraphQL?

GitHub has a nice one too:

 

https://developer.github.com/v4/explorer/

 

Who is using GraphQL?

Also Yelp:

 

https://www.yelp.com/developers/graphql/query/search

 

And many other companies:

 

http://graphql.org/users/

How does it work?

The best way to explain it is describing its principal concepts:

 

Schema

The GraphQL schema defines the server’s API and is written in its own typed language:

 

type Message {
  id: ID!
  text: String!
  author: String!
  comment: String
}

Queries

Defined inside the Schema, Queries in GraphQL are analogous to REST’s GET,  is the way to ask the server for the data we need. Contrary to REST, however, we get full power to ask for exactly what we need, and in the format we need it.


type Query {
  allMessages(): [Message]
}

Mutators

Defined inside the Schema, Mutators could be compared to REST’s POST, PUT and DELETE, is the way to modify data in the server, they allow to create, modify and delete information:

input MessageInput {
    text: String
}

type Mutation {
    updateMessage(id: ID!, input: MessageInput): Message
}

Resolvers

Resolver are external functions mapped to the Schema in charge of processing the queries and mutators, they should process the data, make the writing operations and return the queried information:

const root = {
  allMessages: function (args) {
    return db.getAllMessages()
  },
  updateMessage: function ({id, input}) {
    const currentMessage = db.getMessage(id)

    if (!currentMessage) {
      throw new Error('No message exists with id: ' + id);
    }

    currentMessage.update({text: input})
    return currentMessage
  }
}

References

Keep learning:

 

 

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