Inline if and unless (modifier form) in Ruby - Mini Project: Build & Apply

Inline if and unless (modifier form) in Ruby

📖 Scenario: You are creating a simple program to check if a person is old enough to vote. You want to use Ruby's inline if and unless modifier forms to make your code short and clear.

🎯 Goal: Build a Ruby program that uses inline if and unless modifiers to print messages based on a person's age.

📋 What You'll Learn

Create a variable age with the exact value 20

Create a variable voting_age with the exact value 18

Use inline if modifier to print 'You can vote!' if age is greater than or equal to voting_age

Use inline unless modifier to print 'You cannot vote yet.' if age is less than voting_age

Print the messages exactly as specified

💡 Why This Matters

🌍 Real World

Inline if and unless modifiers help write clean and readable code for simple conditions, like checking user input or status.

💼 Career

Many Ruby developers use these modifiers to keep code concise and easy to understand, especially in web development with frameworks like Ruby on Rails.

1

Create the age variable

Create a variable called age and set it to 20.

Ruby

# Create a variable called age and set it to 20
# Your code here

Hint

Use = to assign the value 20 to the variable age.

2

Create the voting_age variable

Create a variable called voting_age and set it to 18.

Ruby

age = 20
# Create a variable called voting_age and set it to 18
# Your code here

Hint

Use = to assign the value 18 to the variable voting_age.

3

Use inline if modifier to print voting message

Use puts "You can vote!" if age >= voting_age to print the message when age is greater than or equal to voting_age.

Ruby

age = 20
voting_age = 18
# Use inline if modifier to print "You can vote!" if age >= voting_age
# Your code here

Hint

Write the print statement with if at the end to make it inline.

4

Use inline unless modifier to print non-voting message

Use puts "You cannot vote yet." unless age >= voting_age to print the message when age is less than voting_age. Then run the program to see the output.

Ruby

age = 20
voting_age = 18
puts "You can vote!" if age >= voting_age
# Use inline unless modifier to print "You cannot vote yet." unless age >= voting_age
# Your code here

Hint

Use unless at the end of the print statement to check the opposite condition.

Practice

1. What does the following Ruby code do?
puts "Hello" if true

easy

A. Prints "Hello" because the condition is true

B. Prints nothing because the condition is false

C. Raises a syntax error

D. Prints "Hello" only if false

Solution

1. Step 1: Understand the inline if condition

   The code uses if true, so the condition is always true.

2. Step 2: Determine the action based on the condition

   Since the condition is true, puts "Hello" runs and prints "Hello".

3. Final Answer:

   Prints "Hello" because the condition is true -> Option A

4. Quick Check:

   Inline if with true condition prints output [OK]

Hint: If condition is true, inline if runs the code [OK]

Common Mistakes:

• Thinking it prints only if condition is false
• Confusing inline if with inline unless
• Expecting syntax error for inline if

2. Which of the following is the correct syntax for using inline unless in Ruby?

easy

A. puts "No" unless false

B. puts "No" unless

C. puts "No"unless (false)

D. puts "No" unless: false

Solution

1. Step 1: Recall inline unless syntax

   Inline unless requires a condition after the keyword, like unless false.

2. Step 2: Check each option

   puts "No" unless false is valid syntax. puts "No"unless (false) puts "No"unless (false) is invalid due to missing space after the string literal. Options B and D are incomplete or invalid.

3. Final Answer:

   puts "No" unless false -> Option A

4. Quick Check:

   Inline unless needs a condition after it [OK]

Hint: Inline unless needs a condition right after it [OK]

Common Mistakes:

• Omitting the condition after unless
• Using colon instead of space
• Adding unnecessary parentheses

3. What is the output of this Ruby code?

count = 0
count += 1 if false
count += 1 unless false
puts count

medium

A. 0

B. 2

C. 1

D. SyntaxError

Solution

1. Step 1: Evaluate first increment with inline if

   count += 1 if false does not run because condition is false, so count stays 0.

2. Step 2: Evaluate second increment with inline unless

   count += 1 unless false runs because unless false means if true, so count becomes 1.

3. Step 3: Print the final count

   puts count prints 1.

4. Final Answer:

   1 -> Option C

5. Quick Check:

   Inline if false skips, inline unless false runs [OK]

Hint: Inline unless runs when condition is false [OK]

Common Mistakes:

• Thinking inline if false runs the code
• Confusing unless with if
• Expecting count to be 2

4. Identify the error in this Ruby code:

puts "Done" unless

medium

A. Incorrect use of puts

B. Missing condition after unless

C. Should use if instead of unless

D. No error, code runs fine

Solution

1. Step 1: Check the inline unless syntax

   Inline unless requires a condition after it to decide when to run the code.

2. Step 2: Analyze the given code

   The code ends with unless but no condition follows, causing a syntax error.

3. Final Answer:

   Missing condition after unless -> Option B

4. Quick Check:

   Inline unless must have a condition [OK]

Hint: Always put a condition after unless [OK]

Common Mistakes:

• Leaving out the condition after unless
• Thinking puts usage is wrong
• Confusing syntax error with runtime error

5. Given the array nums = [0, 1, 2, 3], which code snippet correctly prints only the non-zero numbers using inline unless?

hard

A. nums.each { |n| puts n if n != 0 }

B. nums.each { |n| puts n if n == 0 }

C. nums.each { |n| puts n unless n != 0 }

D. nums.each { |n| puts n unless n == 0 }

Solution

1. Step 1: Understand the goal

   We want to print numbers except zero, so skip zero and print others.

2. Step 2: Analyze each option

   nums.each { |n| puts n unless n == 0 } uses puts n unless n == 0, which prints n only if n is not zero. nums.each { |n| puts n if n == 0 } prints only zero, which is wrong. nums.each { |n| puts n unless n != 0 } prints only zero because unless n != 0 means if n == 0. nums.each { |n| puts n if n != 0 } prints non-zero numbers but uses inline if, not unless.

3. Final Answer:

   nums.each { |n| puts n unless n == 0 } -> Option D

4. Quick Check:

   Inline unless skips zero, prints others [OK]

Hint: Use unless with condition to skip unwanted values [OK]

Common Mistakes:

• Confusing unless with if
• Printing zero instead of skipping
• Using wrong condition logic