Why would you use a !! operator

Question

I came across abit of ruby in a example

def role?(role)
  return !!self.roles.find_by_name(role.to_s.camelize)
end

Why would you ever use !!? Is it not the same as

 return self.roles.find_by_name(role.to_s.camelize)

Does adding the double exclamation mark add something to the evaluation?

Answer 1

You use it if you only want the boolean, not the object. Any non-nil object except for boolean false represents true, however, you'd return the data as well. By double negating it, you return a proper boolean.

Answer 2

Disclaimer: Not a ruby programmer but having a stab at this.

!!, double bang or "not not", might convert the value to a boolean. One ! returns the boolean opposite and another bang thereafter will flip it to its normal boolean value.