Question

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What does !! mean in ruby?

Hi,

I’m new to Ruby and can’t find anywhere description of what “!!” means.

Here’s an example:

def signed_in?
  !!current_user
end

If this is a double negative, why not to say:

def signed_in?
  current_user
end

Please help.

Answer 1

In most programming languages, including Ruby, ! will return the opposite of the boolean value of the operand. So when you chain two exclamation marks together, it converts the value to a boolean.