Array methods (length, include?, flatten) in Ruby - Mini Project: Build & Apply

Array methods (length, include?, flatten)

📖 Scenario: You are organizing a small library's book collection. The books are grouped by genre, and you want to learn how to use Ruby array methods to explore this collection.

🎯 Goal: Build a Ruby program that uses array methods length, include?, and flatten to find out how many genres there are, check if a specific book is in the collection, and combine all books into one list.

📋 What You'll Learn

Create an array of arrays called library with exact genres and books

Create a variable called genre_count to store the number of genres

Use include? method to check if the book 'The Hobbit' is in the library

Use flatten method to combine all books into one array called all_books

Print the results exactly as instructed

💡 Why This Matters

🌍 Real World

Libraries, bookstores, and personal collections often organize items in groups. Knowing how to count groups, check for items, and combine lists helps manage collections easily.

💼 Career

Understanding array methods is essential for data handling in programming jobs, especially when working with lists, databases, or APIs that return nested data.

1

Create the library array

Create an array called library with these exact genres and books:
[['Fantasy', 'The Hobbit', 'Harry Potter'], ['Science Fiction', 'Dune', 'Neuromancer'], ['Mystery', 'Sherlock Holmes', 'Gone Girl']]

Ruby

# Create the array called library with the given genres and books
# Your code here

Need a hint?

Remember to use square brackets [] to create arrays and separate items with commas.

2

Count the number of genres

Create a variable called genre_count and set it to the length of the library array using the length method.

Ruby

library = [['Fantasy', 'The Hobbit', 'Harry Potter'], ['Science Fiction', 'Dune', 'Neuromancer'], ['Mystery', 'Sherlock Holmes', 'Gone Girl']]
# Create genre_count using library.length
# Your code here

Need a hint?

Use array.length to find how many items are in an array.

3

Check if 'The Hobbit' is in the library

Create a variable called has_hobbit and set it to true or false by checking if the string 'The Hobbit' is included anywhere in the library array using the include? method on a flattened version of library.

Ruby

library = [['Fantasy', 'The Hobbit', 'Harry Potter'], ['Science Fiction', 'Dune', 'Neuromancer'], ['Mystery', 'Sherlock Holmes', 'Gone Girl']]
genre_count = library.length
# Create has_hobbit by checking if 'The Hobbit' is included in the flattened library
# Your code here

Need a hint?

Use flatten to make one array from nested arrays, then use include? to check for an item.

4

Flatten the library and print results

Create a variable called all_books that is the flattened version of library. Then print genre_count, has_hobbit, and all_books each on its own line using puts.

Ruby

library = [['Fantasy', 'The Hobbit', 'Harry Potter'], ['Science Fiction', 'Dune', 'Neuromancer'], ['Mystery', 'Sherlock Holmes', 'Gone Girl']]
genre_count = library.length
has_hobbit = library.flatten.include?('The Hobbit')
# Create all_books as the flattened library
# Print genre_count, has_hobbit, and all_books each on its own line
# Your code here

Need a hint?

Use puts to print each value. Use inspect to print the array as a string.