/graphql-dive-in

Some notes for myself while learning GraphQL

Primary LanguageRuby

GraphQL dive in

Resources

Introduction

What is GraphQL

  • It's a new API standard created as an alternative to REST.
  • Introduced by Facebook in 2012. Announced to the public back in 2015. Open-sourced with many contributors.
  • Other companies, like Netflix (Falcor) and Coursera, where working on similar ideas back then to make API interactions more efficient.
  • When REST was introduced:
    • Clients were simple.
    • Development speed was much slower than today.
  • Facebook decided to create GraphQL because of:
    • Increased mobile usage.
    • Low power devices gaining importance.
    • Sloppy network connections.

Advantages

  • It exposes a single API endpoint that responds exactly with the data requested by the client.
  • It enables declarative data fetching: clients can specify exactly the data they need.
    • Minimizing the amount of data that needs to be transferred over the network. (Solves over-fetching).
    • Limits the requests needed to fetch data for a specific client to 1 (Solves under-fetching).
    • Allowing different client types to use an API tailored to their needs.
    • It's easier to iterate on the fronted (no need to update the API).
  • Introspection in to the data most used by clients.
  • Supports explicit deprecation.
  • Provides aids to instrumentation and performance monitoring.
  • Strong type system (and validation through it).

Core Concepts

  • Schema Definition Language (SDL)

    • Defines the capabilities of the API.
    • Represent the contract between client and server.
    • It's a collection of GraphQL types with special root types: query, mutation and subscription types.
    • Example: 
      type Person {
  name: String!
  age: Int!
  posts: [Post!]
}
type Post {
 title: String!
 author: Person!
}
    • The ! after a type indicates the field is mandatory.

  • Queries

    • Example: 
      {
  allPersons {
    name
  }
}
    • allPersons is the root field of the query.
    • Everyting that follows is the payload of the query.
    • Indicating how to return the last 2. 
      {
  allPersons(last: 2) {
    name
  }
}

  • Mutations

    • Altering the data in the server.
    • 3 types of mutation: creating new data, updating existing data, and deleting existing data.
    • Same structure as queries, but must start with mutation: 
      mutation {
  createPerson(name: "Bob", age: 36) {
    name
    age
  }
}

  • Subscriptions

    • Subscribing to events.
    • Holds a steady connection to the server (stream).
    • Example: 
      subscription {
  newPerson {
    name
    age
  }
}