title: Set varaible in after_action callback
body: <p>Is it possible to set an instance variable in an after_action callback? Becouse I can't find a way to make this work...</p>
  
  <p>Controller</p>
  
  <pre class="lang-rb prettyprint-override"><code>[...]
  after_action :set_var
  [...]
  private
  def set_var
    @myvar = "something"
  end
  [...]
  </code></pre>
  
  <p>But in my view <code>@myvar</code> is always nil.
  If I change <code>after_action</code> with <code>before_action</code> it works, but i really need to set this variable after the action gets executed.</p>