Truthiness (only nil and false are falsy)

Truthiness (only nil and false are falsy)

In Ruby, every value is truthy in a boolean context except nil and false -- notably, unlike many other languages, 0 and "" (empty string) are both truthy. This is a frequent surprise for developers coming from languages where 0 or empty collections are falsy. Knowing this rule precisely avoids subtle conditional bugs.

Warning: Unlike many other languages, 0 and "" (empty string) are truthy in Ruby -- only nil and false are falsy.

Example: Truthiness (only nil and false are falsy)

puts "0 is truthy" if 0
puts "empty string is truthy" if ""
puts "this won't print" if nil
puts "this won't print either" if false