Parent (root) argument in GraphQL - Mini Project: Build & Apply

GraphQL Parent (root) Argument Basics

📖 Scenario: You are building a simple GraphQL API for a bookstore. You want to understand how the parent (also called root) argument works in resolver functions to access data from the previous level in the query.

🎯 Goal: Learn how to use the parent argument in GraphQL resolvers to access data from the root query or from parent fields.

📋 What You'll Learn

Create a root query type with a book field that returns a book object

Add a resolver for book that returns a fixed book object

Add a title field on the book type and a resolver that uses the parent argument to return the title

Add a author field on the book type and a resolver that uses the parent argument to return the author

💡 Why This Matters

🌍 Real World

GraphQL APIs often require accessing data from parent objects to resolve nested fields. Understanding the parent argument is essential for building flexible APIs.

💼 Career

Backend developers working with GraphQL need to write resolvers that use the parent argument to fetch and return nested data correctly.

1

Define the root query with a book field

Create a GraphQL schema with a root Query type that has a book field returning a Book type. Define the Book type with title and author fields of type String.

GraphQL

type Query {
  book: Book
}

type Book {
  title: String
  author: String
}

# Your code here

Need a hint?

Define the root Query type with a book field returning Book. Then define the Book type with title and author fields.

2

Add resolver for book returning a fixed book object

Add a resolver function for the root book field that returns an object with title set to "1984" and author set to "George Orwell".

GraphQL

type Query {
  book: Book
}

type Book {
  title: String
  author: String
}

const resolvers = {
  Query: {
    book: () => {
      // Your code here
    }
  }
}

Need a hint?

Return a fixed object with title and author properties from the book resolver.

3

Add resolver for title using the parent argument

Add a resolver for the title field on the Book type that returns the title property from the parent argument.

GraphQL

type Query {
  book: Book
}

type Book {
  title: String
  author: String
}

const resolvers = {
  Query: {
    book: () => ({ title: "1984", author: "George Orwell" })
  },
  Book: {
    title: (parent) => {
      // Your code here
    }
  }
}

Need a hint?

Use the parent argument to access the title property and return it.

4

Add resolver for author using the parent argument

Add a resolver for the author field on the Book type that returns the author property from the parent argument.

GraphQL

type Query {
  book: Book
}

type Book {
  title: String
  author: String
}

const resolvers = {
  Query: {
    book: () => ({ title: "1984", author: "George Orwell" })
  },
  Book: {
    title: (parent) => parent.title,
    author: (parent) => {
      // Your code here
    }
  }
}

Need a hint?

Use the parent argument to access and return the author property.