title: How to render a batch action in ActiveAdmin including a form?
body: <p>I display a list of trips in admin/trip, for the selected trips I have a batch action which generate a pattern of html code of a newsletter (completed with informations from the selected trips).</p>
  
  <pre><code>batch_action :batch_action, method: :post do |ids|
  
  #my process
  
  render "admin/trips/generate_newsletter.html.erb"
  </code></pre>
  
  <p>That works. However in the view, just before the html code I have a form_tag:</p>
  
  <pre><code>&lt;%= form_tag({action: "batch_action"}, class: "formtastic") do %&gt;
  </code></pre>
  
  <p>The form only contains a text_area where the admin can add a comment for the newsletter. The idea is that when we send the form, the page is refreshed, keeping the trips selected and adding the admin comment into the html code.</p>
  
  <p>Now when I submit the form I get an error: ' Couldn't find batch action "" '.</p>
  
  <p>The variable @_params contains:</p>
  
  <pre><code>{"utf8"=&gt;"✓","authenticity_token"=&gt;"pzqtPMxhB9G83UYad2olCF4O79cK4+mf+R0VBOR61uo=", "admin_text"=&gt;"Admin comment", "commit"=&gt;"Ajouter", "action"=&gt;"batch_action", "controller"=&gt;"admin/trips"}
  </code></pre>
  
  <p>I've tried multiple things but I don't see the answer, maybe what I want to do is impossible this way.</p>