Block syntax (do..end and curly braces) in Ruby - Mini Project: Build & Apply

Block syntax (do..end and curly braces)

📖 Scenario: You are helping a small bakery keep track of daily sales. Each sale has a product name and the quantity sold. You want to use Ruby blocks to process this sales data.

🎯 Goal: Learn how to use Ruby blocks with both do..end and curly braces {} syntax to iterate over sales data and calculate total items sold.

📋 What You'll Learn

Create a hash called sales with exact product names and quantities

Create a variable total_items to hold the sum of all quantities

Use a do..end block with each to add quantities to total_items

Use a curly braces {} block with each to print each product and quantity

Print the total number of items sold

💡 Why This Matters

🌍 Real World

Blocks let you process collections like sales data easily, which is common in business apps.

💼 Career

Understanding block syntax is essential for Ruby developers working on data processing, web apps, and automation.

1

Create the sales data hash

Create a hash called sales with these exact entries: 'Bread' => 10, 'Cake' => 5, 'Pie' => 7

Ruby

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

Hint

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

2

Create a total_items variable

Create a variable called total_items and set it to 0

Ruby

sales = { 'Bread' => 10, 'Cake' => 5, 'Pie' => 7 }
# Create total_items variable and set to 0
# Your code here

Hint

Just write total_items = 0 to start counting from zero.

3

Use a do..end block to sum quantities

Use sales.each do |product, quantity| ... end to add each quantity to total_items

Ruby

sales = { 'Bread' => 10, 'Cake' => 5, 'Pie' => 7 }
total_items = 0
# Use do..end block to add quantities to total_items
# Your code here

Hint

Use each do |product, quantity| ... end to loop through the hash and add quantities.

4

Use curly braces block to print sales and print total

Use sales.each { |product, quantity| puts "#{product}: #{quantity}" } to print each product and quantity. Then print total_items with puts total_items

Ruby

sales = { 'Bread' => 10, 'Cake' => 5, 'Pie' => 7 }
total_items = 0
sales.each do |product, quantity|
  total_items += quantity
end
# Use curly braces block to print each product and quantity
# Then print total_items
# Your code here

Hint

Use curly braces {} with each to print each item. Use puts total_items to show the total.

Practice

1. Which block syntax is generally preferred for multi-line blocks in Ruby?

easy

A. Both are equally preferred for multi-line blocks

B. { }

C. Neither; Ruby does not support blocks

D. do..end

Solution

1. Step 1: Understand block syntax options

   Ruby supports two block syntaxes: do..end and curly braces { }.

2. Step 2: Identify usage for multi-line blocks

   do..end is preferred for multi-line blocks because it improves readability.

3. Final Answer:

   do..end -> Option D

4. Quick Check:

   Multi-line blocks use do..end [OK]

Hint: Use do..end for multi-line blocks, braces for single-line [OK]

Common Mistakes:

• Using curly braces for multi-line blocks reduces readability
• Thinking Ruby doesn't support blocks
• Believing both syntaxes are identical in all cases

2. Which of the following is the correct syntax for a single-line block that prints each number in an array?

easy

A. [1, 2, 3].each { |n| puts n }

B. [1, 2, 3].each { n puts | }

C. [1, 2, 3].each (|n| puts n )

D. [1, 2, 3].each do |n| puts n

Solution

1. Step 1: Identify correct block syntax for single-line

   Single-line blocks use curly braces { } with parameters inside pipes | |.

2. Step 2: Check syntax correctness

   [1, 2, 3].each { |n| puts n } correctly uses { |n| puts n }. Others have syntax errors.

3. Final Answer:

   [1, 2, 3].each { |n| puts n } -> Option A

4. Quick Check:

   Single-line block with braces and pipes [OK]

Hint: Use { |var| ... } for single-line blocks [OK]

Common Mistakes:

• Missing pipes around block parameters
• Using do..end without proper line breaks
• Incorrect placement of pipes or braces

3. What is the output of the following Ruby code?

(1..3).map { |x| x * 2 }

medium

A. [1, 2, 3]

B. [2, 4, 6]

C. [3, 6, 9]

D. SyntaxError

Solution

1. Step 1: Understand the range and map method

   The range (1..3) produces numbers 1, 2, 3. The map method applies the block to each number.

2. Step 2: Calculate each mapped value

   Each number is multiplied by 2, resulting in 2, 4, and 6.

3. Final Answer:

   [2, 4, 6] -> Option B

4. Quick Check:

   Map doubles each element [OK]

Hint: map applies block to each element and returns new array [OK]

Common Mistakes:

• Confusing map with each (which returns original array)
• Expecting a syntax error due to block syntax
• Misunderstanding range behavior

4. Identify the error in this Ruby code:

5.times do |i| puts i }

medium

A. Missing closing end for the block

B. Missing block parameter pipes | |

C. Incorrect use of curly brace to close a do..end block

D. No error, code runs fine

Solution

1. Step 1: Check block opening and closing syntax

   The block starts with do but incorrectly ends with a curly brace }.

2. Step 2: Understand correct block closure

   Blocks opened with do must close with end, not }.

3. Final Answer:

   Incorrect use of curly brace to close a do..end block -> Option C

4. Quick Check:

   do..end blocks cannot close with braces [OK]

Hint: Match do with end, braces with braces [OK]

Common Mistakes:

• Mixing do..end with curly braces
• Forgetting to close the block
• Misplacing block parameter pipes

5. Given the array [1, 2, 3, 4], which block syntax correctly filters even numbers and returns them as a new array?

hard

A. [1, 2, 3, 4].select { |n| n.even? }

B. [1, 2, 3, 4].select do |n| n.even?

C. [1, 2, 3, 4].select { n.even? }

D. [1, 2, 3, 4].select do n.even? end

Solution

1. Step 1: Understand the select method and block parameters

   select filters elements for which the block returns true. The block must receive each element as a parameter.

2. Step 2: Check syntax correctness

   [1, 2, 3, 4].select { |n| n.even? } correctly uses curly braces with block parameter |n| and calls n.even?. [1, 2, 3, 4].select do |n| n.even? has a syntax error (missing end). [1, 2, 3, 4].select { n.even? } misses block parameters. [1, 2, 3, 4].select do n.even? end misses pipes around parameter.

3. Final Answer:

   [1, 2, 3, 4].select { |n| n.even? } -> Option A

4. Quick Check:

   Curly braces with pipes for single-line filter [OK]

Hint: Use { |var| condition } for concise filtering blocks [OK]

Common Mistakes:

• Omitting block parameters
• Mixing do..end without pipes for parameters
• Using incorrect block syntax causing errors