Each as the primary iterator in Ruby - Mini Project: Build & Apply

Using Each as the Primary Iterator in Ruby

📖 Scenario: You work at a small bookstore. You have a list of book titles and their prices. You want to print each book's name with its price to show customers.

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

📋 What You'll Learn

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

Create a variable called discount and set it to 5

Use each as the primary iterator with variables title and price to go through books

Inside the loop, subtract discount from price and store it in final_price

Print each book's title and its final_price in the format: "Ruby Basics costs $20"

💡 Why This Matters

🌍 Real World

This project shows how to loop through collections of data, like products and prices, which is common in many business applications.

💼 Career

Knowing how to use <code>each</code> to iterate over hashes is a fundamental skill for Ruby developers working with data collections.

1

Create the books hash

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

Ruby

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

Hint

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

2

Add a discount variable

Create a variable called discount and set it to 5

Ruby

books = {
  'Ruby Basics' => 25,
  'Rails Guide' => 30,
  'JavaScript Essentials' => 20
}
# Create a variable called discount and set it to 5
# Your code here

Hint

Use a simple assignment to create the variable discount.

3

Use each to iterate over books

Use each as the primary iterator with variables title and price to go through books. Inside the loop, subtract discount from price and store it in final_price

Ruby

books = {
  'Ruby Basics' => 25,
  'Rails Guide' => 30,
  'JavaScript Essentials' => 20
}
discount = 5

# Use each with title and price to iterate over books
# Inside the loop, calculate final_price by subtracting discount from price
# Your code here

Hint

Use books.each do |title, price| ... end to loop. Calculate final_price inside the loop.

4

Print each book's title and final price

Inside the each loop, print each book's title and its final_price in the format: "Ruby Basics costs $20"

Ruby

books = {
  'Ruby Basics' => 25,
  'Rails Guide' => 30,
  'JavaScript Essentials' => 20
}
discount = 5

books.each do |title, price|
  final_price = price - discount
  # Print the title and final_price in the format "Title costs $Price"
  # Your code here
end

Hint

Use puts with string interpolation: "#{title} costs $#{final_price}".

Practice

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

easy

A. It returns a new array with modified items.

B. It runs a block of code once for every item in the array.

C. It changes the array by removing items.

D. It sorts the array in ascending order.

Solution

1. Step 1: Understand the purpose of each

   The each method is used to run a block of code for every item in a collection like an array.

2. Step 2: Check what each does to the array

   It does not change or sort the array; it simply processes each item one by one.

3. Final Answer:

   It runs a block of code once for every item in the array. -> Option B

4. Quick Check:

   each runs code on each item [OK]

Hint: Remember: each processes items, does not change array [OK]

Common Mistakes:

• Thinking each modifies the array
• Confusing each with methods like map
• Assuming each returns a new array

2. Which of the following is the correct syntax to use each on an array numbers to print each number?

easy

A. each numbers { |num| puts num }

B. numbers.each do num puts num end

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

D. numbers.each |num| puts num

Solution

1. Step 1: Identify correct block syntax with each

   The correct syntax uses each followed by a block with { |variable| ... } or do |variable| ... end.

2. Step 2: Check each option

   numbers.each { |num| puts num } uses numbers.each { |num| puts num } which is correct. Others have syntax errors or wrong order.

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 { |item| ... } or each do |item| ... end [OK]

Common Mistakes:

• Writing each numbers instead of numbers.each
• Missing block delimiters like braces or do-end
• Not using pipes | | around block variable

3. What is the output of this Ruby code?

fruits = ['apple', 'banana', 'cherry']
fruits.each { |fruit| puts fruit.upcase }

medium

A. APPLE
BANANA
CHERRY

B. apple
banana
cherry

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

D. Error: undefined method upcase for fruit

Solution

1. Step 1: Understand what each does with puts fruit.upcase

   The each method runs the block for each fruit, printing the uppercase version.

2. Step 2: Check output line by line

   It prints 'APPLE', then 'BANANA', then 'CHERRY' each on a new line.

3. Final Answer:

   APPLE BANANA CHERRY -> Option A

4. Quick Check:

   each prints uppercase fruits [OK]

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

Common Mistakes:

• Thinking each returns a new array
• Expecting lowercase output
• Confusing puts with returning a list

4. What is wrong with this Ruby code snippet?

items = [1, 2, 3]
items.each do item
  puts item * 2
end

medium

A. Array items is empty

B. Using do instead of braces is invalid

C. Cannot multiply numbers inside each

D. Missing pipes around block variable: should be |item|

Solution

1. Step 1: Check block variable syntax in each do block

   When using do with each, the block variable must be inside pipes: do |item|.

2. Step 2: Identify the error

   The code misses pipes around item, causing a syntax error.

3. Final Answer:

   Missing pipes around block variable: should be |item| -> Option D

4. Quick Check:

   Block variables need pipes | | [OK]

Hint: Always put block variables inside | | with each do [OK]

Common Mistakes:

• Omitting pipes around block variables
• Thinking do is invalid with each
• Assuming multiplication inside each is wrong

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, score| puts "#{name.capitalize}: #{score}" }

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

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

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

Solution

1. Step 1: Understand each on a hash

   When using each on a hash, the block receives two variables: key and value.

2. Step 2: Match variables and format output

   The key is the name (symbol), value is the score. Use name.capitalize to print the name nicely.

3. Final Answer:

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

4. Quick Check:

   Hash each uses key, value pairs [OK]

Hint: Hash each block gets two vars: key and value [OK]

Common Mistakes:

• Swapping key and value variables
• Using only one block variable for hash
• Trying to capitalize a number