Flat_map for nested flattening in Ruby - Mini Project: Build & Apply

Flat_map for nested flattening

📖 Scenario: You work at a bakery that sells boxes of assorted cookies. Each box contains different types of cookies in separate trays. You want to list all cookie types available in all boxes in one flat list.

🎯 Goal: Use Ruby's flat_map method to flatten a nested array of cookie trays into a single array of cookie types.

📋 What You'll Learn

Create a variable cookie_boxes that holds an array of arrays, each inner array representing cookie types in a box.

Create a variable all_cookies that uses flat_map on cookie_boxes to flatten all cookie types into one array.

Print the all_cookies array.

💡 Why This Matters

🌍 Real World

Flattening nested lists is common when you have grouped data but want to work with all items together, like listing all products from multiple categories.

💼 Career

Understanding how to flatten nested data structures helps in data processing, report generation, and simplifying complex data for easier use in software development.

1

Create the nested array of cookie trays

Create a variable called cookie_boxes and set it to an array containing these arrays exactly: ["Chocolate Chip", "Oatmeal"], ["Peanut Butter", "Sugar"], and ["Snickerdoodle"].

Ruby

# Create the nested array called cookie_boxes
# Your code here

Need a hint?

Remember to use square brackets for arrays and double quotes for strings.

2

Prepare to flatten the nested array

Create a variable called all_cookies and set it to nil for now. This will hold the flattened list later.

Ruby

cookie_boxes = [["Chocolate Chip", "Oatmeal"], ["Peanut Butter", "Sugar"], ["Snickerdoodle"]]
# Create a variable all_cookies and set it to nil
# Your code here

Need a hint?

Just create the variable and assign nil for now.

3

Use flat_map to flatten the nested array

Set the variable all_cookies to the result of calling flat_map on cookie_boxes with a block that returns each inner array as is.

Ruby

cookie_boxes = [["Chocolate Chip", "Oatmeal"], ["Peanut Butter", "Sugar"], ["Snickerdoodle"]]
all_cookies = nil
# Use flat_map on cookie_boxes to flatten all cookie types into all_cookies
# Your code here

Need a hint?

Use flat_map with a block that takes each tray and returns it.

4

Print the flattened list of cookies

Write a puts statement to print the all_cookies array.

Ruby

cookie_boxes = [["Chocolate Chip", "Oatmeal"], ["Peanut Butter", "Sugar"], ["Snickerdoodle"]]
all_cookies = cookie_boxes.flat_map { |tray| tray }
# Print the all_cookies array
# Your code here

Need a hint?

Use puts all_cookies to print each cookie type on its own line.