[Rails] fields_for inside fields_for

gistfile1.erb

<%= fields_for @tour do |tour_fields| %>
  <%= tour_fields.fields_for :dispatches, @dispatches do |dispatch_fields| %>
    <tr>
      <td><%= if dispatch_fields.object.published? then "Published"; elsif dispatch_fields.object.new_record? then "undefined"; else "Draft"; end%></td>
      <td><%= dispatch_fields.object.dispatch_date %></td>
      <td><%= dispatch_fields.object.venue %></td>
      <td><%= dispatch_fields.object.address%></td>
        <div class="dispatchFields">
          <%= dispatch_fields.hidden_field :id, value: dispatch_fields.object.id unless dispatch_fields.object.id.nil? %>
          <%= dispatch_fields.hidden_field :artist_id, value: current_artist.id %>
          <%= dispatch_fields.hidden_field :activity_type, value: "Event" %>
          <%= dispatch_fields.hidden_field :status, value: dispatch_fields.object.status, :class => "dispatch_status" %>
        </div>
        <div class="dispatchDetailsFields">
          <%= dispatch_fields.fields_for :dispatch_details, dispatch_fields.object.dispatch_details do |dispatch_detail_fields|  %>
            <%= dispatch_detail_fields.hidden_field :id %>
            <%= dispatch_detail_fields.hidden_field :detail_key %>
            <%= dispatch_detail_fields.hidden_field :detail_value%>
          <% end %>
        </div>
      </td>
    </tr>
  <% end %>
<% end %>