Duplicate form fields when using fields_for - ruby-on-rails

Question

I am trying to create a nested form to handle a has_many :through relationship and getting duplicated fields being rendered.
Models
Company
has_many :provides
has_many :services, :through => :provides
accepts_nested_attributes_for :services, :provides
attr_accessible :service_ids
Provide
belongs_to :company
belongs_to :service
Service
has_many :provides
has_many :companies, :through => :provides
has_many :portfolio_items
acts_as_nested_set
Controller
Settings/Services
def index
#company_services = #company.services
#service_list = Service.where("parent_id IS NULL")
end
def show
#user = current_user
# Find features for supplier based users
unless #company.blank?
#my_sectors = #company.sectors
end
end
def update
if params[:company].nil?
#company.service_ids = nil
end
respond_to do |format|
if #company.update_attributes(params[:company])
format.html { redirect_to settings_path, :notice => "Services successfully updated" }
else
format.html { render :index }
end
end
end
Views
Form -
<%= form_for #company, :url => settings_service_path(#company), :method => :put do |f| %>
<div>
<ul>
<% #service_list.each do |item| %>
<%= f.fields_for :provides do |p| %>
<%= p.fields_for :services do |s| %>
<%= render :partial => "subs", :locals => {:subs => s, :service => item, :f => f, :p => p } %>
<% end %>
<% end %>
<% end %>
</ul>
<%= submit_tag("Update") %>
<% end %>
_subs.html.erb
<li>
<%= check_box_tag :service_ids, service.id, #company.services.include?(service), :name => "company[service_ids][]", :class => "checkbox" %>
<%= label_tag service.id, service.service_name %>
<% unless service.children.blank? %>
<ul>
<%= render :partial => "subs", :collection => service.children %>
</ul>
<% end %>
</li>
I know the fields_for is causing the duplication but I don't know why?
Could anybody clarify?

Answer 1

You need to write,
<% #service_list.each do |item| %>
<%= f.fields_for :provides do |p| %>
<%= p.fields_for :services, item do |s| %>
this way fields_for will iterate only for matching service each time.