title: Initialize a session var as array in Rails 3
body: <p>I need to initialize a session var as array.
  Where i do that?</p>
  
  <p>when i try to do this:</p>
  
  <pre><code>session[:complains_id] &lt;&lt; params[:id]
  </code></pre>
  
  <p>i get this message </p>
  
  <blockquote>
    <p>You have a nil object when you didn't expect it!
    You might have expected an instance of Array.
    The error occurred while evaluating nil.&lt;&lt;</p>
  </blockquote>
  
  <p>I know that i have to initialize the var but i dont know where.</p>
  
  <p>Thanks!</p>