title: how to execute an action if the before_action returns false
body: <p>I know that with the following code:</p>
  
  <p><code>before_action :signed_in?, only: [:new]</code></p>
  
  <p>the action <code>new</code> will be executed if the <code>signed_in?</code> returns true, but instead if I want the <code>new</code> action to be executed when <code>signed_in?</code> returns false what do I have to do? Do I have to create a new method called, for instance, <code>not_signed_in?</code>?</p>
  
  <p>Here it is my <code>signed_in?</code> method</p>
  
  <pre><code>def signed_in?
    !@current_user.nil?
  end
  </code></pre>