Delete mutation pattern in GraphQL - Mini Project: Build & Apply

Delete Mutation Pattern in GraphQL

📖 Scenario: You are building a simple GraphQL API for a library system. The system stores books with their id, title, and author. You want to allow users to delete a book by its id.

🎯 Goal: Create a GraphQL delete mutation called deleteBook that takes a book id as input and returns the deleted book's id and title.

📋 What You'll Learn

Define a Book type with id, title, and author fields

Create a deleteBook mutation that accepts an id argument of type ID!

The mutation should return the deleted book's id and title

Implement resolver logic to remove the book from the data store

💡 Why This Matters

🌍 Real World

Deleting records is a common operation in APIs, such as removing users, products, or posts. This pattern helps maintain data integrity and user control.

💼 Career

Understanding how to implement delete mutations is essential for backend developers working with GraphQL APIs in real-world applications.

1

Define the Book type and initial data

Create a GraphQL type Book with fields id (ID!), title (String!), and author (String!). Also, create an array called books with these exact entries: { id: "1", title: "1984", author: "George Orwell" }, { id: "2", title: "Brave New World", author: "Aldous Huxley" }, and { id: "3", title: "Fahrenheit 451", author: "Ray Bradbury" }.

GraphQL

# Define the Book type and create the books array
# Your code here

Need a hint?

Use the type keyword to define the Book type. Create a JavaScript array named books with the exact book objects.

2

Add the deleteBook mutation to the schema

Add a type Mutation to the GraphQL schema with a deleteBook mutation. It should accept an id argument of type ID! and return a Book.

GraphQL

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

const typeDefs = gql`
  type Book {
    id: ID!
    title: String!
    author: String!
  }

  # Add the Mutation type with deleteBook mutation here
  # Your code here
`;

const books = [
  { id: "1", title: "1984", author: "George Orwell" },
  { id: "2", title: "Brave New World", author: "Aldous Huxley" },
  { id: "3", title: "Fahrenheit 451", author: "Ray Bradbury" }
];

Need a hint?

Define a Mutation type with a deleteBook field that takes id: ID! and returns a Book.

3

Implement the deleteBook resolver logic

Create a resolvers object with a Mutation field. Implement the deleteBook resolver that takes parent, args, and removes the book with the matching id from the books array. Return the deleted book object.

GraphQL

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

const typeDefs = gql`
  type Book {
    id: ID!
    title: String!
    author: String!
  }

  type Mutation {
    deleteBook(id: ID!): Book
  }
`;

const books = [
  { id: "1", title: "1984", author: "George Orwell" },
  { id: "2", title: "Brave New World", author: "Aldous Huxley" },
  { id: "3", title: "Fahrenheit 451", author: "Ray Bradbury" }
];

// Add the resolvers object with deleteBook mutation resolver
// Your code here

Need a hint?

Use findIndex to locate the book by id. Use splice to remove it and return the removed book.

4

Export the schema and resolvers for the server

Export the typeDefs and resolvers objects using module.exports so they can be used to create the GraphQL server.

GraphQL

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

const typeDefs = gql`
  type Book {
    id: ID!
    title: String!
    author: String!
  }

  type Mutation {
    deleteBook(id: ID!): Book
  }
`;

const books = [
  { id: "1", title: "1984", author: "George Orwell" },
  { id: "2", title: "Brave New World", author: "Aldous Huxley" },
  { id: "3", title: "Fahrenheit 451", author: "Ray Bradbury" }
];

const resolvers = {
  Mutation: {
    deleteBook(parent, args) {
      const index = books.findIndex(book => book.id === args.id);
      if (index === -1) return null;
      const deleted = books.splice(index, 1)[0];
      return deleted;
    }
  }
};

// Export typeDefs and resolvers
// Your code here

Need a hint?

Use module.exports to export both typeDefs and resolvers.