17. Build a Simple Inventory System with Classes
1. Hello, World!
2. Rename Photos by Capture Date
3. Organize Downloads Folder by File Type
4. Delete Old Log Files Automatically
5. Find Duplicate Files Using MD5 Hashing
6. Generate Comprehensive File Inventory
7. Parse Web Server Logs for Performance Metrics
8. Extract Emails, URLs, and Phone Numbers from Text
9. Track Daily and Monthly Active Users from Apache Logs
10. Generate Formatted Text Reports with Column Alignment
11. Analyze Sales Transactions and Generate Revenue Reports
12. Clean and Validate CSV Data
13. Convert JSON API Responses to CSV
14. Parse and Validate Configuration Files
15. Build a CLI Calculator with Argument Parsing
16. Parse and Display Weather Data from JSON
17. Build a Simple Inventory System with Classes
18. Generate Markdown Table from CSV Data
19. Aggregate Sales Data by Time Period
20. Recursive Directory Size Calculator with Filtering
21. Parse and Transform Server Configuration
22. Find and Replace Across Multiple Files
23. Build a Simple Template Engine
24. CSV Data Validator with Business Rules
25. Build a Multi-Format Log Analyzer

Challenge

Problem

Object-oriented programming is fundamental to building maintainable Ruby applications. This drill teaches you to design classes with initialization, instance methods, state management, and data validation. You'll create an inventory system that tracks products with names, quantities, and prices, learning class design, attr_accessor usage, instance variables, and methods that modify object state—essential skills for building real-world Ruby applications.

Difficulty: Intermediate

Instructions

  1. Create a Product class with:
    • Initialize with name, quantity (default 0), price (default 0.0)
    • Attributes: name (read-only), quantity, price
    • add_stock(amount) method - increases quantity
    • remove_stock(amount) method - decreases quantity, returns false if insufficient
    • total_value method - returns quantity * price
    • in_stock? method - returns true if quantity > 0
    • to_s method - returns formatted string
  2. Create an Inventory class with:
    • Initialize with empty products array
    • add_product(product) method
    • find_product(name) method - returns product or nil (case-insensitive)
    • total_inventory_value method - sum of all products' total_value
    • list_products method - returns array of product strings
  3. Read commands from inventory.txt and execute them
  4. Print final inventory report

Files

Editable
Read-only

Hints

Hint 1

attr_reader :name creates a getter method for @name

Hint 2

attr_accessor :quantity creates both getter and setter for @quantity

Hint 3

Use @variable for instance variables inside classes

Hint 4

array.find { |item| condition } returns first matching item

Hint 5

Use .downcase for case-insensitive string comparison

Hint 6

array.sum(&:method_name) sums results of calling method on each item

Hint 7

Format price with '%.2f' % number for 2 decimal places

Ruby 3.4

Provided Files (Read-only)

1. Correct inventory report

Input: 
process_inventory('inventory.txt')
Expected Output: 
INVENTORY REPORT
==================================================
Laptop: Qty 12 @ $999.99 each (Total: $11999.88)
Mouse: Qty 55 @ $29.99 each (Total: $1649.45)
Keyboard: Qty 30 @ $79.99 each (Total: $2399.70)
--------------------------------------------------
Total Inventory Value: $16049.03

2. Product class works

Input: 
p = Product.new('Test', 10, 5.00)
p.add_stock(5)
puts p.to_s
Expected Output: 
Test: Qty 15 @ $5.00 each (Total: $75.00)

3. Remove stock returns false if insufficient

Input: 
p = Product.new('Test', 5, 10.00)
puts p.remove_stock(10)
puts p.quantity
Expected Output: 
false
5
+ 6 hidden test cases