save has-many associations

I have the following association

class Document < ActiveRecord::Base   has_many :sections   has_many :items, :through => :sections end class Section < ActiveRecord::Base   belongs_to :document   has_many :items end class Item < ActiveRecord::Base   belongs_to :section end

Here is the sample view for the 'new' action <% form_for(@document) do |f| %>   <%= f.error_messages %>   <p>     <p> Header <p/><br />     <%= f.label :hdrcomment %>     <%= f.text_field :hdrcomment %>   </p>   <% for section in @document.sections %>      <% f.fields_for section, :index => section do |s| %>       <%= section.seqnum %><br />       <% for item in section.items %>          <% s.fields_for item, :index => item do |i| %>             <%= i.text_area :comments %><br />          <% end %>       <% end %>      <% end %>   <% end %>   <p>     <%= f.submit "Submit Document" %>   </p> <% end %>

What is way to save the header, sections and items. Do I have to iterate the request hash. The below code doesn't work. Gives ActiveRecord::UnknownAttributeError inDocumentsController#create

def create @document = Document.new(params[:document]) @document.save! end

Request: {"commit"=>"Submit Document", "authenticity_token"=>"+uOqJn1DSjzK6r1iIkaIqZa9VrKpU2Yr/A6zP0vg0eM=", "document"=>{"section"=>{"#<Section:0xb74045f4>"=>{"item"=>{"#<Item:0xb73d2860>"=>{"comments"=>"asdf"}, "#<Item:0xb73d1af0>"=>{"comments"=>"sdf"}}}, "#<Section:0xb7403794>"=>{"item"=>{"#<FeedbackItem:0xb73ce6fc>"=>{"comments"=>"sdf"}}}, "#<Section:0xb740ea90>"=>{"item"=>{"#<Item:0xb73e0e74>"=>{"comments"=>"asd"}}}}, "hdrcomment"=>" asdf"}}

Thanks much.