How to convert an object to Boolean in Ruby?

Question

Ruby objects have some methods for representation in another type, such as:

• to_s: convert to string
• to_a: convert to array
• to_i: convert to whole
• to_f: convert to float

But there is no standard method to convert an object to boolean, nor in the class Object. How to make this conversion?

Answer 1

The idiomatic way to convert an object of any type to Boolean in Ruby is by using a double negation (also called double bang in the Ruby community):

def to_b(obj)
  !!obj
end

The double negation does not affect the value, such that:

!!true  => true
!!false => false

Remember that in Ruby, everything is true except nil and false. Therefore:

to_b "olá" => true
to_b 0     => true
to_b ""    => true
to_b true  => true
to_b nil   => false
to_b false => false