Group_by for categorization in Ruby - Mini Project: Build & Apply

Group_by for categorization

📖 Scenario: You work at a bookstore that wants to organize books by their genre to make it easier for customers to find what they like.

🎯 Goal: You will create a Ruby program that groups a list of books by their genre using the group_by method.

📋 What You'll Learn

Create an array of hashes called books with each book having :title and :genre keys

Create a variable called grouped_books to store the result of grouping books by genre using group_by

Print the grouped_books variable to show books categorized by genre

💡 Why This Matters

🌍 Real World

Grouping items by category is common in apps like bookstores, music libraries, or inventory systems to help users find things easily.

💼 Career

Understanding how to group data efficiently is important for software developers working with collections, databases, or data analysis.

1

Create the books array

Create an array called books with these exact hashes: { title: 'The Hobbit', genre: 'Fantasy' }, { title: '1984', genre: 'Dystopian' }, { title: 'The Catcher in the Rye', genre: 'Classic' }, { title: 'The Lord of the Rings', genre: 'Fantasy' }, { title: 'Brave New World', genre: 'Dystopian' }

Ruby

# Create the books array with the given hashes
# Your code here

Need a hint?

Use square brackets [] to create an array and curly braces {} for each book hash.

2

Prepare to group books by genre

Create a variable called grouped_books and set it to nil for now as a placeholder.

Ruby

books = [
  { title: 'The Hobbit', genre: 'Fantasy' },
  { title: '1984', genre: 'Dystopian' },
  { title: 'The Catcher in the Rye', genre: 'Classic' },
  { title: 'The Lord of the Rings', genre: 'Fantasy' },
  { title: 'Brave New World', genre: 'Dystopian' }
]

# Create a variable called grouped_books and set it to nil
# Your code here

Need a hint?

This step sets up a variable to hold the grouped result later.

3

Group the books by genre

Use the group_by method on the books array to group books by their :genre key. Assign the result to the variable grouped_books.

Ruby

books = [
  { title: 'The Hobbit', genre: 'Fantasy' },
  { title: '1984', genre: 'Dystopian' },
  { title: 'The Catcher in the Rye', genre: 'Classic' },
  { title: 'The Lord of the Rings', genre: 'Fantasy' },
  { title: 'Brave New World', genre: 'Dystopian' }
]

# Use group_by on books to group by :genre and assign to grouped_books
# Your code here

Need a hint?

Use group_by { |book| book[:genre] } to group books by genre.

4

Print the grouped books

Write a puts statement to print the grouped_books variable so you can see the books grouped by genre.

Ruby

books = [
  { title: 'The Hobbit', genre: 'Fantasy' },
  { title: '1984', genre: 'Dystopian' },
  { title: 'The Catcher in the Rye', genre: 'Classic' },
  { title: 'The Lord of the Rings', genre: 'Fantasy' },
  { title: 'Brave New World', genre: 'Dystopian' }
]

grouped_books = books.group_by { |book| book[:genre] }

# Print the grouped_books variable
# Your code here

Need a hint?

Use puts grouped_books to display the grouped result.