Passing a form object to a partial within a fields_for using observe_field

I’m a Rails newbie, so please bear with me. I’m using version 3.0.0.

I have a form to create and update articles which uses a fields_for to
nest a ‘collaborator’ resource, of which an article :has_many. I
would like for users to be able to search for other users to add as
collaborators (co-authors of the article) using a live search field
linked to a select box (or something similar).

Unfortunately, I need to pass the original article form object to the
search results partial on every AJAX request in the live search. Is
there any simple way to do this, or a better approach entirely?

Here’s my code:

Following the nested model Railscast, my articles form includes this

<%= f.fields_for :collaborations do |builder| %> <%= render 'collaboration_fields', :f => builder %> <% end %>

<%= link_to_add_fields "Add another collaborator", f, :collaborations %>

The collaboration_fields partial includes an observe_field (obtrusive
as it may be…) call to handle the live search functionality:

Search for collaborator: <%= render :partial => 'live_search' %> <%= link_to_remove_fields "Remove collaborator", f %>
<%= observe_field "live_user_search_form", :url => { :controller => 'articles', :action => 'live_search' }, :frequency => 0.5, :update => 'live_search_results', :with => "'search_text=' + escape(value)", :loading => "document.getElementById('spinner').style.display='inline'", :loaded => "document.getElementById('spinner').style.display='none'" %>

And the live_search partial just allows the user to select from the
search results:

<% if @live_search_users && @live_search_users.hits.count > 0 %>
<%= :collaborator_id, { |hit| ["#{hit.instance.first_name}
#{hit.instance.last_name} (#{})",] }, { :include_blank => true } %>
<% else %>
<%= :collaborator_id, { |hit| ["#{hit.first_name}
#{hit.last_name} (#{})",] }, { :include_blank =>
true } %>
<% end %>

The searching is handled through a live_search function in the
articles controller:

def live_search
if request.xhr?
if params[‘search_text’].strip.length > 0
terms = params[‘search_text’].split.collect do |word|
@live_search_users = User ) do
keywords terms
render :partial => ‘/articles/live_search’
render :partial => ‘/articles/live_search’

As you can see the live_search partial requires the article form, f,
for the select function, but obviously that’s not available unless
passed somehow. I’ve tried passing it around using :locals in every
place I can think of, such as from the observe_field call through the
controller and back to the partial, but nothing seems to work.

Any help or guidance would be greatly appreciated!