fields_for not nested

fields_for_not_nested.html.rb

<%= form_tag 'topics/edit_all' do %>
  <% @topics.each do |topic| %> 
    <%= fields_for "topics[]", topic do |f| %>
      <%= f.check_box :enabled %>
      <%= f.label topic["name"] %><br />
    <% end %>
  <% end %>
  <%= submit_tag %>
<% end %>