Context argument in GraphQL - Mini Project: Build & Apply

Using the Context Argument in GraphQL Resolvers

📖 Scenario: You are building a simple GraphQL API for a bookstore. You want to use the context argument in your resolvers to access user information for authorization.

🎯 Goal: Create a GraphQL resolver that uses the context argument to check if a user is logged in before returning the list of books.

📋 What You'll Learn

Create a books array with three books, each having id and title.

Create a context object with a user property set to { name: 'Alice' }.

Write a resolver function called getBooks that takes parent, args, and context as arguments.

Inside getBooks, check if context.user exists; if yes, return the books array.

If context.user does not exist, return an empty array.

💡 Why This Matters

🌍 Real World

Using the context argument in GraphQL resolvers is essential for managing user authentication and authorization in real-world APIs.

💼 Career

Understanding how to access and use context in GraphQL is a key skill for backend developers working with modern API technologies.

1

Create the books data array

Create an array called books with these exact objects: { id: 1, title: '1984' }, { id: 2, title: 'Brave New World' }, and { id: 3, title: 'Fahrenheit 451' }.

GraphQL

// Create the books array with 3 book objects
// Your code here

Need a hint?

Use const books = [ ... ] to create the array with the exact book objects.

2

Create the context object with user info

Create a constant called context and set it to an object with a user property equal to { name: 'Alice' }.

GraphQL

const books = [
  { id: 1, title: '1984' },
  { id: 2, title: 'Brave New World' },
  { id: 3, title: 'Fahrenheit 451' }
];

// Create the context object with user info
// Your code here

Need a hint?

Use const context = { user: { name: 'Alice' } } to create the context object.

3

Write the getBooks resolver using context

Write a function called getBooks that takes parent, args, and context as parameters. Inside, check if context.user exists. If yes, return the books array.

GraphQL

const books = [
  { id: 1, title: '1984' },
  { id: 2, title: 'Brave New World' },
  { id: 3, title: 'Fahrenheit 451' }
];

const context = { user: { name: 'Alice' } };

// Write the getBooks resolver function
// Your code here

Need a hint?

Define function getBooks(parent, args, context) and use if (context.user) to check user presence.

4

Complete getBooks to return empty array if no user

Add an else clause to getBooks that returns an empty array [] if context.user does not exist.

GraphQL

const books = [
  { id: 1, title: '1984' },
  { id: 2, title: 'Brave New World' },
  { id: 3, title: 'Fahrenheit 451' }
];

const context = { user: { name: 'Alice' } };

function getBooks(parent, args, context) {
  if (context.user) {
    return books;
  }
  // Add else clause to return empty array
  // Your code here
}

Need a hint?

Use else { return [] } to handle the case when no user is present.