Resolver organization in GraphQL - Mini Project: Build & Apply

Organizing GraphQL Resolvers for a Bookstore

📖 Scenario: You are building a simple GraphQL API for a bookstore. The API needs to provide information about books and authors.To keep your code clean and easy to maintain, you want to organize your GraphQL resolvers properly.

🎯 Goal: Build a well-organized set of GraphQL resolvers separated by type (Query, Book, Author) to fetch book and author data.

📋 What You'll Learn

Create a books array with 3 books, each having id, title, and authorId

Create an authors array with 2 authors, each having id and name

Create a resolvers object with three keys: Query, Book, and Author

In Query, add a resolver books that returns the books array

In Book, add a resolver author that returns the author object matching the book's authorId

In Author, add a resolver books that returns all books written by that author

💡 Why This Matters

🌍 Real World

Organizing resolvers by type is a common practice in real GraphQL APIs to keep code modular and easy to understand.

💼 Career

Understanding resolver organization is essential for backend developers working with GraphQL to build scalable and maintainable APIs.

1

Create the initial data arrays

Create an array called books with these exact objects: { id: '1', title: '1984', authorId: 'a1' }, { id: '2', title: 'Animal Farm', authorId: 'a1' }, and { id: '3', title: 'Brave New World', authorId: 'a2' }. Also create an array called authors with these exact objects: { id: 'a1', name: 'George Orwell' } and { id: 'a2', name: 'Aldous Huxley' }.

GraphQL

# Your code here

Hint

Use const books = [...] and const authors = [...] to create the arrays with the exact objects.

2

Create the resolver object with Query type

Create a resolvers object. Inside it, add a Query object with a resolver function books that returns the books array.

GraphQL

const books = [
  { id: '1', title: '1984', authorId: 'a1' },
  { id: '2', title: 'Animal Farm', authorId: 'a1' },
  { id: '3', title: 'Brave New World', authorId: 'a2' }
];

const authors = [
  { id: 'a1', name: 'George Orwell' },
  { id: 'a2', name: 'Aldous Huxley' }
];

const resolvers = {
  Query: {
    // Your code here
  }
};

Hint

Inside resolvers, add Query: { books: () => books } to return the books array.

3

Add the Book type resolver for author

Inside the resolvers object, add a Book object. Add a resolver function author that takes book as an argument and returns the author object from authors whose id matches book.authorId.

GraphQL

const books = [
  { id: '1', title: '1984', authorId: 'a1' },
  { id: '2', title: 'Animal Farm', authorId: 'a1' },
  { id: '3', title: 'Brave New World', authorId: 'a2' }
];

const authors = [
  { id: 'a1', name: 'George Orwell' },
  { id: 'a2', name: 'Aldous Huxley' }
];

const resolvers = {
  Query: {
    books: () => books
  },
  Book: {
    // Your code here
  }
};

Hint

Use Book: { author: (book) => authors.find(author => author.id === book.authorId) } inside resolvers.

4

Add the Author type resolver for books

Inside the resolvers object, add an Author object. Add a resolver function books that takes author as an argument and returns an array of books from books whose authorId matches author.id.

GraphQL

const books = [
  { id: '1', title: '1984', authorId: 'a1' },
  { id: '2', title: 'Animal Farm', authorId: 'a1' },
  { id: '3', title: 'Brave New World', authorId: 'a2' }
];

const authors = [
  { id: 'a1', name: 'George Orwell' },
  { id: 'a2', name: 'Aldous Huxley' }
];

const resolvers = {
  Query: {
    books: () => books
  },
  Book: {
    author: (book) => authors.find(author => author.id === book.authorId)
  },
  Author: {
    // Your code here
  }
};

Hint

Use Author: { books: (author) => books.filter(book => book.authorId === author.id) } inside resolvers.