Inline if and unless (modifier form) in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of inline if modifier

What will be the output of this Ruby code snippet?

Ruby

message = "Hello"
message += " World" if message.length < 10
puts message

A Hello World

B Hello

C HelloWorld

D Error

💡 Hint

Check the length of the string before the condition.

The condition checks if the length of 'message' is less than 10, which is true (5). So ' World' is added.

❓ Predict Output

intermediate

Using inline unless modifier

What will this Ruby code print?

Ruby

count = 5
count -= 1 unless count > 5
puts count

A 4

B 5

C 6

D Error

💡 Hint

Remember 'unless' runs the code only if the condition is false.

Since count (5) is not greater than 5, the condition is false, so count is decreased by 1.

🔧 Debug

advanced

Identify the error in inline if usage

Which option shows the code that will raise a syntax error?

A puts "Done" if true; puts "Not done"

B puts "Done" if true

C puts "Done" unless false

D puts "Done" if true else puts "Not done"

💡 Hint

Inline if cannot be combined with else in this way.

Option D tries to use 'else' with inline if, which is invalid syntax in Ruby.

🧠 Conceptual

advanced

Effect of inline unless modifier

What is the value of variable 'status' after running this code?

Ruby

status = "active"
status = "inactive" unless status == "inactive"

A "active"

B "inactive"

C nil

D Error

💡 Hint

The 'unless' runs the assignment only if the condition is false.

Since status is "active", which is not "inactive", the assignment runs and status becomes "inactive".

❓ Predict Output

expert

Output with inline if and method call

What will this Ruby code output?

Ruby

def check(num)
  puts "Even" if num.even?
  puts "Odd" unless num.even?
end
check(3)

A Even\nOdd

B Even

C Odd

D Error

💡 Hint

Check what num.even? returns for 3.

3 is odd, so num.even? is false. The first puts is skipped, the second runs printing 'Odd'.

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