I am ussing attribute_fu for multiple forms.

But, if I edit a Story and then add a new Play and add multiple Sounds to that new, unsaved Play, they all have an ID of "-1":
  story[play_attributes][new][-1][sound_attributes][new][-1][name]

And because of that only one of them is actually passed on as params and saved.

If I save my Play first, they will get fine numbering, -1, -2, -3.

## models
class Story
   has_many :plays, :attributes => true

class Play
   has_many :sounds, :attributes => true

## story/edit.html.erb
<% form_for :story, :url => { :action => 'update', :id => @story } do |f| %>
<div id="plays">
   <%= f.render_associated_form(@story.plays) %>
 </div>
<% end %>

## story/_play.html.erb
   <div class="sounds">
     <%= f.render_associated_form(play.sounds) %>
   </div>
   <%= f.add_associated_link('Ny route', play.sounds.build, :expression => "$(this).previous('.sounds')") %>

## story/_sound.html.erb
   <div class="sounds">
    <%= f.render_associated_form(play.sounds) %>
   </div>
   <%= f.add_associated_link('Ny lyd', play.sounds.build, :expression => "$(this).previous('.sounds')") %>