13. Convert JSON API Responses to CSV
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

Developers extract GitHub statistics for non-technical stakeholders who work in Excel, marketing needs social media metrics in spreadsheets, and finance requires payment data from APIs in CSV format. This drill teaches you to read nested JSON from provided files (simulating API responses), extract fields from complex structures, flatten to tabular format, and generate CSV output—bridging the API world with the spreadsheet world.

Difficulty: Intermediate

Instructions

  1. Read JSON file containing array of GitHub repository objects
  2. Extract fields from nested structures:
    • Repository name, description, stars, forks
    • Owner name (nested in owner object)
    • Created date (parse and format as YYYY-MM-DD)
    • Language, open issues count
  3. Flatten nested data to tabular format
  4. Generate CSV string with headers
  5. Output summary: Total repos: X, Total stars: Y, Most popular: Z
  6. Return the CSV string

Files

Editable
Read-only

Hints

Hint 1

JSON.parse(File.read(file)) parses JSON from file

Hint 2

Access nested values with hash['key']['nested_key']

Hint 3

Date.parse(string).strftime('%Y-%m-%d') formats the date

Hint 4

Build CSV manually: values.join(',')

Hint 5

Use .sum { |r| r['stars'] } to total stars

Hint 6

max_by { |r| r['stars'] } finds the most popular repo

Ruby 3.4

Provided Files (Read-only)

1. Correct summary output

Input: 
convert_json_to_csv('repos.json')
Expected Output: 
Converted 3 repositories
Total stars: 8,350
Most popular: awesome-ruby (5,000 stars)

2. CSV has correct headers

Input: 
csv = convert_json_to_csv('repos.json')
puts csv.lines.first.strip
Expected Output: 
Converted 3 repositories
Total stars: 8,350
Most popular: awesome-ruby (5,000 stars)
Name,Description,Owner,Stars,Forks,Language,Open_Issues,Created

3. Extracts nested owner

Input: 
csv = convert_json_to_csv('repos.json')
puts csv.lines[1].split(',')[2]
Expected Output: 
Converted 3 repositories
Total stars: 8,350
Most popular: awesome-ruby (5,000 stars)
user1
+ 2 hidden test cases