autocomplete on edit

Is the normal autocomplete supposed to pull from the DB what is in the
field when doing an edit or is there something else that needs to be
done to get it to show up while doing an edit?

I provide a Javascript array, using this method:

def users_list
  @users = User.find( :all, :order => 'username' )
  headers[' content-type' ] = ' text/javascript'
  render :action => 'users_list', :layout => false
end

and this view:

var users = new Array(<%= @users.size %>);
<% @users.each_with_index do |user, index| -%>
users[<%= index %>] = '<%= user.username %>';
<% end -%>