title: Retrieve hidden field in form_for
body: <p>I want to retrieve hidden field in a form for.
  Here is my form :</p>
  
  <pre><code>&lt;%= bootstrap_form_for :cvs do |f| %&gt;
      &lt;%= f.text_field :nom, label: "Nom du nouveau CV", :required =&gt; true %&gt;
      &lt;%= f.hidden_field :cvuse, :value =&gt; params[:user] %&gt;
      &lt;%= f.submit class: "btn btn-primary"%&gt;
  &lt;% end %&gt;
  </code></pre>
  
  <p>When I check my server logs I could see my variable passed :</p>
  
  <pre><code>Started POST "/cvs" for 127.0.0.1 at 2015-08-31 14:30:36 +0200
  Processing by CvsController#create as HTML
  Parameters: {"utf8"=&gt;"✓", "authenticity_token"=&gt;"someCrazyKey", "cvs"=&gt;{"nom"=&gt;"dd", "cvuse"=&gt;"1"}, "commit"=&gt;"Save Cvs"}
  Unpermitted parameter: cvuse
  </code></pre>
  
  <p>Do you know how I could retrieve this variable <code>cvuse</code>. just for precision this form execute the <code>create</code> method in my controller.</p>