Truthy and falsy values (only nil and false are falsy) in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are the only falsy values in Ruby?

In Ruby, only false and nil are falsy. Everything else is truthy.

beginner

Is the number 0 truthy or falsy in Ruby?

The number 0 is truthy in Ruby, unlike some other languages where it might be falsy.

beginner

What will this Ruby code print?<br>

if nil
  puts 'Yes'
else
  puts 'No'
end

It will print No because nil is falsy in Ruby.

intermediate

Why does Ruby treat only false and nil as falsy?

Ruby's design makes it simple: only false and nil mean 'no' or 'nothing'. Everything else counts as 'yes' or 'something'.

intermediate

How can understanding truthy and falsy values help you write better Ruby code?

Knowing which values are truthy or falsy helps you write clear conditions and avoid bugs, especially in if statements and loops.

Which of these is falsy in Ruby?

A nil

B 0

C "" (empty string)

D [] (empty array)

Only nil and false are falsy in Ruby. All others, including 0, empty strings, and empty arrays, are truthy.

What does this code print?<br>

puts false ? 'Yes' : 'No'

A No

B nil

C false

D Yes

Since false is falsy, the ternary operator chooses the else part, printing No.

Is the string "false" truthy or falsy in Ruby?

A Causes error

B Falsy

C Depends on context

D Truthy

Any string, even "false", is truthy in Ruby.

Which values will make an if condition run its block in Ruby?

A Only true

B Only non-zero numbers

C Anything except false and nil

D Only non-empty strings

Ruby treats everything except false and nil as true in conditions.

What is the result of !!nil in Ruby?

A true

B false

C nil

D Error

Double negation converts nil to false.

Explain which values are considered falsy in Ruby and why this matters when writing conditions.

Think about what Ruby treats as 'no' or 'nothing'.

Describe how Ruby's truthy and falsy values differ from other languages you might know.

Consider languages where 0 or empty strings might be falsy.