Each for iteration in Ruby - Mini Project: Build & Apply

Using Each For Iteration in Ruby

📖 Scenario: You work in a small bookstore. You have a list of book titles and their prices. You want to print each book's name and price to share with your team.

🎯 Goal: Build a Ruby program that uses each with for iteration to go through a hash of books and prices, then print each book and its price.

📋 What You'll Learn

Create a hash called books with exact keys and values

Create a variable called total_price and set it to 0

Use for title, price in books.each to iterate over the hash

Add each price to total_price

Print each book title and price inside the loop

After the loop, print the total price

💡 Why This Matters

🌍 Real World

Bookstores and shops often need to list items with prices and calculate totals for sales or inventory.

💼 Career

Knowing how to iterate over collections and sum values is a basic skill for many programming jobs, especially in retail or data processing.

1

Create the books hash

Create a hash called books with these exact entries: 'Ruby Basics' => 25, 'JavaScript Guide' => 30, 'Python 101' => 20

Ruby

# Create the books hash with exact entries
# Your code here

Hint

Use curly braces {} to create a hash with keys and values separated by =>.

2

Create a total price variable

Create a variable called total_price and set it to 0

Ruby

books = { 'Ruby Basics' => 25, 'JavaScript Guide' => 30, 'Python 101' => 20 }
# Create total_price variable and set to 0
# Your code here

Hint

Use = to assign 0 to total_price.

3

Use each for iteration to sum prices and print books

Use for title, price in books.each to iterate over the books hash. Inside the loop, add price to total_price and print the book title and price using puts with the format: "Title: #{title}, Price: $#{price}"

Ruby

books = { 'Ruby Basics' => 25, 'JavaScript Guide' => 30, 'Python 101' => 20 }
total_price = 0
# Use for each iteration to add prices and print books
# Your code here

Hint

Use for title, price in books.each to loop. Use total_price += price to add prices. Use puts with string interpolation to print.

4

Print the total price

After the loop, print the total price using puts with the format: "Total price: $#{total_price}"

Ruby

books = { 'Ruby Basics' => 25, 'JavaScript Guide' => 30, 'Python 101' => 20 }
total_price = 0
for title, price in books.each
  total_price += price
  puts "Title: #{title}, Price: $#{price}"
end
# Print the total price
# Your code here

Hint

Use puts after the loop to print the total price with string interpolation.

Practice

1. What does the each method do in Ruby when used with an array?

easy

A. It removes duplicate elements from the array.

B. It runs the given block once for every element in the array.

C. It sorts the array in ascending order.

D. It returns the length of the array.

Solution

1. Step 1: Understand the purpose of each

   The each method is used to loop over every element in a collection like an array.

2. Step 2: Identify what happens inside the block

   The block given to each runs once for each element, allowing actions on each item.

3. Final Answer:

   It runs the given block once for every element in the array. -> Option B

4. Quick Check:

   each repeats actions per item [OK]

Hint: Remember: each runs code for every item in the list [OK]

Common Mistakes:

• Confusing each with sorting or filtering methods
• Thinking each returns a new array
• Assuming each counts elements

2. Which of the following is the correct syntax to iterate over an array numbers using each in Ruby?

easy

A. numbers.each do num puts num end

B. each numbers do |num| puts num end

C. numbers.each { |num| puts num }

D. numbers.each(num) { puts num }

Solution

1. Step 1: Recognize correct each syntax

   The each method is called on the array, followed by a block with a parameter inside pipes.

2. Step 2: Check block format

   numbers.each { |num| puts num } uses curly braces with a block parameter |num| and a valid block body puts num.

3. Final Answer:

   numbers.each { |num| puts num } -> Option C

4. Quick Check:

   Correct block syntax = numbers.each { |num| puts num } [OK]

Hint: Use .each with {|var| ...} or do |var| ... end [OK]

Common Mistakes:

• Placing the variable outside the pipes
• Calling each without a block
• Using parentheses incorrectly with each

3. What will be the output of this Ruby code?

fruits = ['apple', 'banana', 'cherry']
fruits.each do |fruit|
  puts fruit.upcase
end

medium

A. APPLE
BANANA
CHERRY

B. apple
banana
cherry

C. APPLE BANANA CHERRY

D. ['APPLE', 'BANANA', 'CHERRY']

Solution

1. Step 1: Understand the each loop behavior

   The code loops over each fruit and prints the uppercase version using puts fruit.upcase.

2. Step 2: Determine output format

   puts prints each string on a new line, so each fruit name appears uppercase on its own line.

3. Final Answer:

   APPLE BANANA CHERRY -> Option A

4. Quick Check:

   each + puts prints each item on a new line [OK]

Hint: puts prints each item on a new line inside each [OK]

Common Mistakes:

• Expecting output on one line
• Confusing puts with print
• Not applying upcase method

4. Identify the error in this Ruby code snippet:

numbers = [1, 2, 3]
numbers.each do num
  puts num * 2
end

medium

A. Missing pipes around the block variable 'num'.

B. Incorrect method name; should be 'for' instead of 'each'.

C. Missing parentheses after 'each'.

D. Using 'puts' inside the block is not allowed.

Solution

1. Step 1: Check block variable syntax

   In Ruby, block variables must be enclosed in pipes like |num| when using do...end.

2. Step 2: Identify the missing pipes

   The code uses do num instead of do |num|, causing a syntax error.

3. Final Answer:

   Missing pipes around the block variable 'num'. -> Option A

4. Quick Check:

   Block variables need pipes |var| [OK]

Hint: Always put block variables inside |pipes| with do...end [OK]

Common Mistakes:

• Omitting pipes around block variables
• Thinking parentheses are required after each
• Believing puts cannot be used inside blocks

5. Given a hash scores = { alice: 10, bob: 15, carol: 12 }, how can you use each to print each name and score in the format Name: Score?

hard

A. scores.each { |name| puts "#{name.capitalize}: #{score}" }

B. scores.each { |score, name| puts "#{name}: #{score}" }

C. scores.each do |name| puts "#{name}: #{scores[name]}" end

D. scores.each do |name, score| puts "#{name.capitalize}: #{score}" end

Solution

1. Step 1: Understand hash iteration with each

   When iterating a hash with each, two block variables receive the key and value respectively.

2. Step 2: Use correct variable order and string formatting

   scores.each do |name, score| puts "#{name.capitalize}: #{score}" end correctly uses |name, score| and prints with #{name.capitalize}: #{score}.

3. Final Answer:

   scores.each do |name, score| puts "#{name.capitalize}: #{score}" end -> Option D

4. Quick Check:

   Hash each uses two vars: key, value [OK]

Hint: Hash each needs two vars: |key, value| [OK]

Common Mistakes:

• Swapping key and value variables
• Using only one block variable for hash
• Not capitalizing the name correctly