Avoid unnecessary uses of `!!`

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Metadata

ID: ruby-best-practices/no-double-negation

Language: Ruby

Severity: Info

Category: Best Practices

Description

The !! operator in Ruby is often used to convert a value to a boolean. However, this operator can be overused and lead to unnecessary complexity in your code. In many cases, the !! operator is not needed because Ruby already treats nil and false as falsy values, and everything else as truthy.

Overuse of the !! operator can make the code harder to read and understand. It can also potentially introduce bugs if used incorrectly. For example, !! before a variable that could be nil can lead to unexpected NoMethodError exceptions.

To avoid this, only use the !! operator when you specifically need to convert a non-boolean value to a boolean. If you’re just using it in an if condition or similar, you can often omit it. For example, instead of writing if !!user, you can write if user. Remember, clear and simple code is often the most effective.

Non-Compliant Code Examples

def my_method
  do_something if !!foo

  var = 'foo'
  if !!var
    # body omitted
  end
end

Compliant Code Examples

class Foo
  def logged_in?
    !!@active_user
  end
end