Boolean values (true, false, nil) in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Ruby code?

Consider the following Ruby code snippet. What will it print when run?

Ruby

value = nil
if value
  puts "true branch"
else
  puts "false branch"
end

A true branch

B SyntaxError

C false branch

D nil

💡 Hint

Remember that in Ruby, only false and nil are treated as false in conditionals.

In Ruby, nil is treated as false in conditionals, so the else branch runs.

❓ Predict Output

intermediate

What does this expression return?

What is the value of the variable result after running this Ruby code?

Ruby

result = (false || nil) && true

A nil

B false

C true

D SyntaxError

💡 Hint

Recall how Ruby evaluates && and || with false and nil.

Ruby evaluates false || nil as nil because false is falsey, so it returns the second operand. Then nil && true returns nil because nil is falsey.

🔧 Debug

advanced

Why does this code raise an error?

This Ruby code raises an error. What is the cause?

Ruby

def check_value(val)
  if val == true || val == false || val == nil
    puts "Valid boolean or nil"
  else
    puts "Invalid value"
  end
end

check_value(nil)

A NoMethodError because nil has no == method

B SyntaxError due to incorrect use of || operator

C TypeError because nil cannot be compared with ==

D No error; code runs and prints "Valid boolean or nil"

💡 Hint

Check how Ruby compares values with == and how nil behaves.

The code runs without error because == works with nil and booleans. The condition is true for nil, so it prints "Valid boolean or nil".

❓ Predict Output

advanced

What is the output of this Ruby code involving nil and boolean?

What does this Ruby code print?

Ruby

value = false
puts value || "default"

A default

B nil

C false

D true

💡 Hint

Remember how || returns the first truthy value.

Since false is falsey, value || "default" returns "default".

🧠 Conceptual

expert

Which Ruby value is treated as false in conditionals?

In Ruby, which of the following values are treated as false in conditional expressions?

A Only false

B Both false and nil

C false, nil, and 0

D Only nil

💡 Hint

Think about what Ruby considers falsey.

In Ruby, only false and nil are falsey. Everything else, including 0, is truthy.