Intro to

GraphQL

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Sabin Marcu

Software Engineer at R/GA

Been working in web since '09

React Dev since 2015

React trainer @ JSLeague

Whoami

Overview

Intro to GraphQL

Agenda

Async Resolve Functions

Nested Queries

Usage with Prisma

RootQuery Entry Points

Bidirectional Relations

Circular References

Introduction

Language and Entities

REST-ful Routing

GraphQL Schemas

Root Queries

The GraphiQL Tool

Introduction

Intro to GraphQL

What is it?

a syntax that describes how to ask for data

Intro to GraphQL

It lets the client specify exactly what data it needs

It makes it easier to aggregate data from multiple sources

It uses a type system to describe data

Why?

Intro to GraphQL

Language and Entities

Intro to GraphQL

Type System

{
  hero {
    name
    appearsIn
  }
}

{
  "data": {
    "hero": {
      "name": "R2-D2",
      "appearsIn": [
        "NEWHOPE",
        "EMPIRE",
        "JEDI"
      ]
    }
  }
}

Object types and fields

Intro to GraphQL

type Character {
  name: String!
  appearsIn: [Episode!]!
}

object type

fields

Intro to GraphQL

type Character {
  name: String!
  appearsIn: [Episode!]!
}

String = scalar type, can't have sub-selections in the query

String! = non-nullable

[Episode!]! = non-nullable array of Episode objects

Intro to GraphQL

Arguments

type Starship {
  id: ID!
  name: String!
  length(unit: LengthUnit = METER): Float
}

argument

Intro to GraphQL

3 root operations

type Query {
    ... query operations ...
}
type Mutation {
    ... mutation operations ...
}
type Subscription {
    ... subscription operations ...
}

Intro to GraphQL

type Query {
  hero(episode: Episode): Character
  droid(id: ID!): Droid
}

query {
  hero {
    name
  }
  droid(id: "2000") {
    name
  }
}

{
  "data": {
    "hero": {
      "name": "R2-D2"
    },
    "droid": {
      "name": "C-3PO"
    }
  }
}

Intro to GraphQL

Scalar types

Int, Float, String, Boolean, ID
custom: Date
special: Enums

Entity types

type Character {
  name: String!
  appearsIn: [Episode!]!
}

Intro to GraphQL

Interfaces

interface Character {
  id: ID!
  name: String!
  friends: [Character]
  appearsIn: [Episode]!
}

type Human implements Character {
  id: ID!
  name: String!
  friends: [Character]
  appearsIn: [Episode]!
  starships: [Starship]
  totalCredits: Int
}

type Droid implements Character {
  id: ID!
  name: String!
  friends: [Character]
  appearsIn: [Episode]!
  primaryFunction: String
}

Intro to GraphQL

Union types

union SearchResult = Human | Droid | Starship

{
  search(text: "an") {
    __typename
    ... on Human {
      name
      height
    }
    ... on Droid {
      name
      primaryFunction
    }
    ... on Starship {
      name
      length
    }
  }
}

{
  "data": {
    "search": [
      {
        "__typename": "Human",
        "name": "Han Solo",
        "height": 1.8
      },
      {
        "__typename": "Human",
        "name": "Leia Organa",
        "height": 1.5
      },
      {
        "__typename": "Starship",
        "name": "TIE Advanced x1",
        "length": 9.2
      }
    ]
  }
}

Intro to GraphQL

Input types

input ReviewInput {
  stars: Int!
  commentary: String
}

mutation CreateReviewForEpisode($ep: Episode!, $review: ReviewInput!) {
  createReview(episode: $ep, review: $review) {
    stars
    commentary
  }
}

{
  "data": {
    "createReview": {
      "stars": 5,
      "commentary": "This is a great movie!"
    }
  }
}

Q&A

JavaScript Beyond the Basics

Intro to

GraphQL

What is it?

Why?

Thank you!