Handling More Complex Data Queries in Apollo Server 4

Welcome to the lesson on "Handling More Complex Data Queries," as part of the "Comprehensive Intro to GraphQL in TypeScript" course. In this lesson, we'll expand on what we learned about mutations in the previous lesson. We'll focus on setting up nested queries in GraphQL to handle more intricate relationships between data, specifically authors and books.

To handle nested queries, we need a schema that represents our data types and their relationships.

1. Define Data Types

   We'll create Author and Book types with fields that reference each other:

   import { ApolloServer } from '@apollo/server';
   
   const typeDefs = `#graphql
     type Author {
       id: ID!
       name: String!
       books: [Book]
     }
   
     type Book {
       id: ID!
       title: String!
       author: Author
     }
   
     type Query {
       books: [Book]
       authors: [Author]
     }
   `;

   • Author has fields id, name, and books, which is an array of Book.
   • Book has fields id, title, and an author, which is of type Author.

2. Sample Data

   Define some sample data to work with:

   const authors = [
     { id: '1', name: 'J.R.R. Tolkien' },
     { id: '2', name: 'J.K. Rowling' }
   ];
   
   const books = [
     { id: '1', title: 'The Hobbit', author: '1' },
     { id: '2', title: 'Harry Potter', author: '2' }
   ];

   This data will be used to simulate a small library.

Resolvers are responsible for fetching the data defined in your schema.

1. Define Resolvers

   Here's how you can write resolvers to handle nested queries:

   const resolvers = {
     Query: {
       books: () => books,
       authors: () => authors
     },
     Book: {
       author: (book: any) => authors.find(author => author.id === book.author)
     },
     Author: {
       books: (author: any) => books.filter(book => book.author === author.id)
     }
   };

   • The Query resolvers return the sample data for books and authors.
   • The Book resolver finds the author of a given book.
   • The Author resolver filters books written by a given author.

2. Initialize Apollo Server

   Combine the schema and resolvers to set up the server:

   import { startStandaloneServer } from '@apollo/server/standalone';
   
   const server = new ApolloServer({ typeDefs, resolvers });
   
   const { url } = await startStandaloneServer(server, { listen: { port: 4000 } });
   console.log(`🚀 Server ready at ${url}`);

   When you run your server.ts file, it should print:

   🚀 Server ready at http://localhost:4000/