Hierarchical Nested Form

_child_fields.html.erb

    <%= f.text_area :label, :rows => 2%>

    <%= field_set_tag 'Answers' do %> 
      <%= f.fields_for :answers do |af| %>
        <%= af.text_field :label %>
        <%= af.collection_select(:followup_id, f.object.children, :id, :label, :include_blank => true) %>
        <%= af.link_to_remove 'X', :class => 'radius button'%>
      <% end %>

      <%= f.link_to_add "Add Answer", :answers%>
    <% end %>

_form.html.erb

  <%= nested_form_for [@survey, @question] do |f| %>
    <%= render :partial => "child_fields", :locals => {:f => f} %>

    <%= field_set_tag 'Follow-up' do %> 
      <%= f.fields_for :children %>
      <%= f.link_to_add "Add Followup", :children, :class => 'radius button two'%>
    <% end %>

    <%= f.submit  %>
  <% end %>

answer_fields_blueprint

<div id="answers_fields_blueprint" style="display: none"><div class="fields">
  <input id="question_answers_attributes_new_answers_label" name="question[answers_attributes][new_answers][label]" size="30" type="text">
  <select id="question_answers_attributes_new_answers_followup_id" name="question[answers_attributes][new_answers][followup_id]"><option value=""></option>
<option value="38">Followup Question 2</option></select>
  <input id="question_answers_attributes_new_answers__destroy" name="question[answers_attributes][new_answers][_destroy]" type="hidden" value="false">
  <a href="javascript:void(0)" class="radius button remove_nested_fields" data-association="answers">X</a>
</div>