Authenticity Token being created differently when using render_to_string

Question

I'm generating a small form through render_to_string and for some reason the CSRF token is not being generated correctly (i.e. it's different from the header and the user is logged out on submit, along with a "Can't verify CSRF token" on the logs). Here's the relevant code:

Controller:

def publish
  @question = @event.questions.find(params[:id])
  @question.update_attribute(:published, true) unless @question.published?
  Pusher[@event.to_param].trigger('new_question', question: render_question)
  redirect_to event_path(@event)
end


private
  def render_question
    render_to_string('questions/_unanswered_question', locals: {question: @question}, layout: false)
  end
  def fetch_event
    @event ||= current_user.events.find(params[:event_id])
  end

I'm using Pusher, but you can assume this is just being rendered on the page with this Javascript:

$("#questions").append(data.question); // data is what I send from Pusher.

And finally, the partial being rendered:

.answer
  = form_for [@event, question, question.answers.new] do |f|
    %h2
      = question.title

    %ul
      - (1..5).each do |n|
        - if question.send("answer_#{n}").present?
          %li
            = f.radio_button :option, n, id: "q_#{question.id}_answer_option_#{n}"
            = f.label question.send("answer_#{n}"), for: "q_#{question.id}_answer_option_#{n}"

    %p
      = f.submit "Answer"

This works just fine without being appended to the page, but rendered within the layout. Note that this is not a remote form.

Answer 1

It looks like you are generating the form using ajax and then adding it to the Dom. The csrf token is generated new for every request. As far as I know, you have to use the csrf token which is available in the header and replace the one in the form with it using js.

Should look something like this:

success: ()->
  parameter = $("meta[name=csrf-param]").attr("content")
  token     = $("meta[name=csrf-token]").attr("content")
  question  = $(data.question).find("[name="+parameter+"]").val(token)

Currently I have no computer to test that first, so hopefully I am right :/