Boolean values (true, false, nil) in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to assign the boolean value true to the variable.

Ruby

is_valid = [1]

Drag options to blanks, or click blank then click option'

Anil

Bfalse

Ctrue

DTrue

Attempts:

3 left

💡 Hint

Common Mistakes

Using capitalized True instead of true

Using false or nil instead of true

In Ruby, the boolean value for true is true (all lowercase).

2fill in blank

medium

Complete the code to assign the boolean value false to the variable.

Ruby

is_active = [1]

Drag options to blanks, or click blank then click option'

ATrue

Bfalse

Cnil

DFalse

Attempts:

3 left

💡 Hint

Common Mistakes

Using capitalized False instead of false

Using true or nil instead of false

In Ruby, the boolean value for false is false (all lowercase).

3fill in blank

hard

Fix the error in the code by replacing the incorrect nil value.

Ruby

result = [1]

Drag options to blanks, or click blank then click option'

Atrue

Bnil

CTrue

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing nil with false

Using capitalized True or true incorrectly

Here, false is the correct boolean value to use instead of nil if you want a boolean false.

4fill in blank

hard

Fill both blanks to create a condition that checks if a variable is nil or false.

Ruby

if value == [1] || value == [2]
  puts "Value is false or nil"
end

Drag options to blanks, or click blank then click option'

Anil

Bfalse

Ctrue

DNone

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'None' instead of nil

Using true instead of false

To check if a variable is either nil or false, use both values in the condition.

5fill in blank

hard

Fill all three blanks to create a hash that maps keys to boolean or nil values.

Ruby

status = { success: [1], error: [2], pending: [3] }

Drag options to blanks, or click blank then click option'

Atrue

Bfalse

Cnil

DTrue

Attempts:

3 left

💡 Hint

Common Mistakes

Using capitalized True or False

Using strings instead of boolean values

Confusing nil with false

This hash uses Ruby boolean values true, false, and nil correctly.

Practice

1. In Ruby, which of the following represents a value that means "nothing" or "no value"?

easy

A. nil

B. true

C. false

D. 0

Solution

1. Step 1: Understand the meaning of nil

   In Ruby, nil is used to represent the absence of any value, like an empty box.

2. Step 2: Compare with other options

   true and false are Boolean values meaning yes or no, but not "no value". 0 is a number, not a special value for nothing.

3. Final Answer:

   nil -> Option A

4. Quick Check:

   nil means no value [OK]

Hint: Remember: nil means no value or empty box [OK]

Common Mistakes:

• Confusing false with nil
• Thinking 0 means no value
• Mixing true and nil meanings

2. Which of the following is the correct way to write a Boolean false value in Ruby?

easy

A. False

B. FalseValue

C. FALSE

D. false

Solution

1. Step 1: Recall Ruby syntax for Boolean values

   Ruby uses lowercase true and false for Boolean values.

2. Step 2: Check each option

   False and FALSE are not valid Ruby keywords. FalseValue is not a keyword but a name.

3. Final Answer:

   false -> Option D

4. Quick Check:

   Boolean false is lowercase false [OK]

Hint: Boolean keywords are lowercase in Ruby [OK]

Common Mistakes:

• Using capitalized False or TRUE
• Adding extra words to Boolean values
• Confusing symbols with keywords

3. What will the following Ruby code print?

value = nil
if value
  puts "Yes"
else
  puts "No"
end

medium

A. nil

B. Yes

C. No

D. Error

Solution

1. Step 1: Understand how Ruby treats nil in conditions

   In Ruby, nil is treated as false in conditions.

2. Step 2: Follow the if-else logic

   Since value is nil, the if value condition is false, so the else branch runs, printing "No".

3. Final Answer:

   No -> Option C

4. Quick Check:

   nil acts as false in if [OK]

Hint: nil and false both act as false in conditions [OK]

Common Mistakes:

• Thinking nil is true
• Expecting nil to print itself
• Confusing nil with empty string

4. Find the error in this Ruby code snippet:

if false
  puts "No"
elsif nil
  puts "Maybe"
else
  puts "Yes"
end

medium

A. The condition elsif nil never runs

B. No error, prints "Yes"

C. The code prints "Maybe" incorrectly

D. Syntax error: missing end

Solution

1. Step 1: Check syntax correctness

   The code has matching if, elsif, and end, so no syntax error.

2. Step 2: Evaluate conditions in order

   false is false, nil is also false, so both conditions fail and else runs, printing "Yes".

3. Final Answer:

   No error, prints "Yes" -> Option B

4. Quick Check:

   False and nil skip to else [OK]

Hint: False and nil conditions skip to else branch [OK]

Common Mistakes:

• Thinking elsif nil runs
• Expecting syntax error
• Confusing elsif with else

5. You want to check if a variable status is either true or nil in Ruby. Which condition correctly does this?

hard

A. if status == true || status == nil

B. if status == true && status == nil

C. if status || nil

D. if status != false

Solution

1. Step 1: Understand the condition requirements

   You want to check if status is either true OR nil, so use logical OR (||).

2. Step 2: Analyze each option

   if status == true || status == nil uses status == true || status == nil, which matches the requirement. if status == true && status == nil uses AND, which can never be true for both at once. if status || nil is incorrect syntax and logic. if status != false checks if status is not false, which includes other values too.

3. Final Answer:

   if status == true || status == nil -> Option A

4. Quick Check:

   Use OR (||) to check either condition [OK]

Hint: Use || to check if either condition is true [OK]

Common Mistakes:

• Using && instead of ||
• Confusing != false with true or nil
• Writing invalid condition syntax