Software Engineering :: API :: Architectural Style :: GraphQL :: Training :: Learning GraphQL :: 4. Creating a GraphQL Server Schema

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Software Engineering :: API :: Architectural Style :: GraphQL :: Training :: Learning GraphQL :: 4. Creating a GraphQL Server Schema

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4. Creating a GraphQL Server Schema

Introducing the GraphQL schema definition language

A language which defines all of our APIs types

GraphQL Scalar Types

• Int
• Float
• String
• Boolean
• ID

example

id: ID!
name: String!

GraphQL Object Types

Container of Scalar and other Object Types

type Photo {
  id: ID!
  name: String!
  url: String!
  description: String
  rating: Float
  private: Boolean!
}

Nullable vs. Non-nullable

!: value must be non-null

name: String!
description: String

Root Queries

type Query {
  totalUsers: Int!
}

Lists

type User {
  postedPhotos: [Photo!]!
}

Nullable vs. Non-nullable Lists

• photos: [Photo]: Nullable list of nullable values
• photos: [Photo]!: Non-nullable list of nullable values
• photos: [Photo!]!: Non-nullable list of non-nullable values (empty array is valid)

Setting up a GraphQL server with Apollo Server

» npm init -y
» npm install graphql apollo-server nodemon
» code .

index.js

const { ApolloServer, gql } = require('apollo-server');

const typeDefs = gql`
  type Query {
    totalDays: Int!
  }
`;

// const resolvers = {};

const server = new ApolloServer({
  typeDefs,
  mocks: true,
});

server
  .listen()
  .then(({ url }) =>
    console.log(`Server running at ${url}`)
  );

package.json

{
  "name": "ski-day-counter",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "start": "nodemon ."
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "apollo-server": "^2.25.0",
    "graphql": "^15.5.0",
    "nodemon": "^2.0.7"
  }
}

Start Server

» npm start

Playground

Query for Mock Data

Creating a custom object

index.js

Define an Object Type

const { ApolloServer, gql } = require('apollo-server');

const typeDefs = gql`
  type SkiDay {
    id: ID!
    date: String!
    mountain: String!
  }
  
  type Query {
    totalDays: Int!
    allDays: [SkiDay!]!
  }
`;

// const resolvers = {};

const server = new ApolloServer({
  typeDefs,
  mocks: true,
});

server
  .listen()
  .then(({ url }) =>
    console.log(`Server running at ${url}`)
  );

Query allDays

query {
  totalDays
  allDays {
    id
    date
    mountain
  }
}

Adding an enumeration type

index.js

Adding an enumeration type

const { ApolloServer, gql } = require('apollo-server');

const typeDefs = gql`
  type SkiDay {
    id: ID!
    date: String!
    mountain: String!
    conditions: Conditions
  }
  
  enum Conditions {
    POWDER
    HEAVY
    ICE
    THIN
  }
  
  type Query {
    totalDays: Int!
    allDays: [SkiDay!]!
  }
`;

// const resolvers = {};

const server = new ApolloServer({
  typeDefs,
  mocks: true,
});

server
  .listen()
  .then(({ url }) =>
    console.log(`Server running at ${url}`)
  );

Query conditions

query {
  totalDays
  allDays {
    id
    date
    mountain
    conditions
  }
}

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