Using accepts_nested_attributes_for on a join table with its own attributes - Duplicate rows

I have the following three models (Rails 2.3.8)

    class Outbreak < ActiveRecord::Base
        has_many :incidents, :dependent => :destroy
        has_many :locations, :through => :incidents

        accepts_nested_attributes_for :incidents, :allow_destroy => true
        accepts_nested_attributes_for :locations, :allow_destroy => true, :reject_if => proc { |attrs| attrs.all? { |k, v| v.blank? } }

    end

   class Incident < ActiveRecord::Base
        belongs_to :outbreak
        belongs_to :location
   end


   class Location < ActiveRecord::Base
 has_many :incidents
 has_many :outbreaks, :through => :incidents

     accepts_nested_attributes_for :incidents, :allow_destroy => true

   end

The parameters from the form seem to be ok

"outbreak"=>{ "locations_attributes"=>{"0"=>{"lon"=>"-1.39", "placename"=>"wetwe", "hpu_id"=>"15", "postcode"=>"so1 1aa", "region_id"=>"10", "address_1"=>"", "town"=>"Bargate", "address_2"=>"", "address_3"=>"", "lat"=>"50.89"}},"incidents_attributes"=>{"0"=>{"subtype_id"=>"7", "category_id"=>"1", "detail"=>"", "subcategory_id"=>"2"}} }

But when the Outbreak is saved 3 rows are created in the Incidents table (the join table) and a single row in the Outbreak and Location tables.

The rows in the Incidents table are not fully populated from the params as follows:

id outbreak_id location_id category_id subcategory_id subtype_id detail  created_at    updated_at 

 57 23   NULL     1       2           7 开发者_运维知识库                         2010-11-25 14:45:18.385905  2010-11-25 14:45:18.385905 
 58 23   27         NULL       NULL        NULL    NULL           2010-11-25 14:45:18.39828  2010-11-25 14:45:18.39828 
 59 23   27         NULL         NULL     NULL      NULL           2010-11-25 14:45:18.403051  2010-11-25 14:45:18.403051 

This must be due to the either the format of the parameters or the multiple accepts_nested_attributes_for methods - how do I have just a single row being entered in the Incidents table with all of the parameters information?

Second time so far this week I've answered my own question ^^ that'll teach me to put more effort in before giving up and posting on the net for help,

Still after looking at my original question I didn't include enough information to answer it properly - the issue (apart from the set up of the models) was down to the Outbreak constructor in the Outbreak controller new method,

Original Outbreaks_controller

def new

    @outbreak = Outbreak.new
    @outbreak.risks.build
    //links locations directly to Outbreak instead of through Incidents
    @outbreak.locations.build
    @outbreak.incidents.build

    respond_to do |format|
      format.html # new.html.erb
      format.xml  { render :xml => @outbreak }
    end
end

Revised Outbreaks_controller

def new

    @outbreak = Outbreak.new
    @outbreak.risks.build
    //builds Incidents then a Location through that incident
    @outbreak.incidents.build.build_location

    respond_to do |format|
      format.html # new.html.erb
      format.xml  { render :xml => @outbreak }
    end
end

Changes to the three models

    class Outbreak < ActiveRecord::Base
        has_many :incidents, :dependent => :destroy
        has_many :locations, :through => :incidents

        accepts_nested_attributes_for :incidents, :allow_destroy => true


    end

   class Incident < ActiveRecord::Base
        belongs_to :outbreak
        belongs_to :location

        accepts_nested_attributes_for :location, :allow_destroy => true
   end


   class Location < ActiveRecord::Base
       has_many :incidents
       has_many :outbreaks, :through => :incidents

   end

This seems to work ok - also posted the create action and main form

The create action only needs the nested params provided for :outbreak (the models do the work).

def create

    @outbreak = Outbreak.new(params[:outbreak])
    @outbreak.user_id = current_user.id

        respond_to do |format|
     if @outbreak.save
        flash[:notice] = 'Outbreak was successfully created.'
        format.html { redirect_to(@outbreak) }
        format.xml  { render :xml => @outbreak, :status => :created, :location => @outbreak }
      else
        format.html { render :action => "new" }
        format.xml  { render :xml => @outbreak.errors, :status => :unprocessable_entity }
      end
    end
end

The outbreak form is pretty long so I've cut it down to the two sections mentioned (although there's probably more attributes and fields here than is need to get an idea).

An example of the HTML element id for the nested fields can be found at the bottom in the Javascript observe_field helper. A post I made on AJAX updates of nested_attributes_for partials might also be useful AJAX update of accepts_nested_attributes_for

    <% form_for(@outbreak, :html => {:multipart => true}) do |form| %>
    <%= form.error_messages %>
    <div id="tabs">
        <ul>

            <li ><a href="#tabs_b">Outbreak</a></li>
            <li ><a href="#tabs_c">Location</a></li>

        </ul>   


            <div id="tabs_b">
                <fieldset id="b" class="form_div">
                    <legend>Outbreak</legend>

                    <fieldset>
                        <legend>References</legend>
                      <div class="left_form">
                        <%= form.label :user_reference %>
                      </div>
                      <div class="right_form">
                        <%= form.text_field :user_reference %>
                      </div>
                      <div style="clear:both;"></div>

                    </fieldset>

                </fieldset>
            </div>
            <div id="tabs_c">
                <fieldset id="c" class="form_div" >

                    <legend>Location</legend>
                      <div id="location_error"></div>
                            <fieldset>
                            <legend>Setting</legend>
                <% form.fields_for :incidents do |incident_form| %>

                                  <div class="left_form">
                                    <%= incident_form.label :category_id %>
                                  </div>

                                  <div class="right_form">
                                    <div id="incident_category_select">
                                    <%= render :partial => 'category_select', :locals => {:categories => @categories, :incident_form => incident_form} %>
                                    </div>
                                  </div>
                                  <div style="clear:both;"></div>

                                  <div class="left_form">
                                    <%= incident_form.label :subcategory_id %>
                                  </div>
                                  <div class="right_form">
                                    <div id="incident_subcategory_select">
                                    <%= render :partial => 'subcategory_select', :locals => { :subcategories => @subcategories, :incident_form => incident_form } %>
                                    </div>
                                  </div>
                                  <div style="clear:both;"></div>
                                  <div class="left_form">
                                    <%= incident_form.label :subtype_id %>
                                  </div>
                                  <div class="right_form">
                                    <div id="incident_subtype_select">
                                    <%= render :partial => 'subtype_select',  :locals => { :subtypes => @subtypes, :incident_form => incident_form } %>
                                    </div>
                                  </div>
                                  <div style="clear:both;"></div>
                                  <div id="cuisine_div">
                                    <% if @outbreak.outbreak_type == "FOODBORNE" %>
                                        <div class="left_form">
                                            <%= label :incident, :cuisine_id %>
                                        </div>
                                        <div class="right_form">
                                            <% cuisine_select = (@incident != nil ? @incident.cuisine_id.to_i : '') %>
                                            <%= incident_form.select( :cuisine_id, "<option value='' >Please select</option>" + options_from_collection_for_select(@cuisines, :id, :name, cuisine_select)) %>
                                        </div>
                                    <% end %>

                                  </div>
                                  <div style="clear:both;"></div>
                                  <div class="left_form">
                                    <%= incident_form.label :detail %>
                                  </div>
                                  <div class="right_form">
                                    <%= incident_form.text_field :detail %>
                                  </div>


                        </fieldset>
                        <fieldset>
                            <legend>Details</legend>
                            <%  incident_form.fields_for :location do |location_form| %>
                                  <div style="clear:both;"></div>
                                   <div class="left_form">
                                    <%= location_form.label :placename %>
                                  </div>
                                  <div class="right_form">
                                    <%= location_form.text_field :placename %>
                                  </div> 
                                  <div style="clear:both;"></div>
                                  <div class="left_form">
                                    <%= location_form.label :address_1 %>
                                  </div>
                                  <div class="right_form">
                                    <%= location_form.text_field :address_1 %>
                                  </div>
                                  <div style="clear:both;"></div>
                                  <div class="left_form">
                                    <%= location_form.label :address_2 %>
                                  </div>
                                  <div class="right_form">
                                    <%= location_form.text_field :address_2 %>
                                  </div>
                                  <div style="clear:both;"></div>
                                  <div class="left_form">
                                    <%= location_form.label :address_3 %>
                                  </div>
                                  <div class="right_form">
                                    <%= location_form.text_field :address_3 %>
                                  </div> 
                                  <div style="clear:both;"></div>
                                  <div class="left_form">
                                    <%= location_form.label :town %>
                                  </div>
                                  <div class="right_form">
                                    <%= location_form.text_field :town %>
                                  </div>
                                  <div style="clear:both;"></div>
                                  <div class="left_form">
                                    <%= location_form.label :postcode %>
                                  </div>
                                  <div class="right_form">
                                    <%= location_form.text_field :postcode %>
                                  </div>
                                  <div style="clear:both;"></div>        
                                  <div class="left_form">
                                    <%= location_form.label :region_id %>
                                  </div>
                                  <div class="right_form" >
                                        <% region_select = (@location != nil ? @location.region_id.to_i : '') %>
                                    <%= location_form.select(:region_id, "<option value=''>Select a region</option>" + options_from_collection_for_select(@regions, :id, :name, region_select)) %>
                                  </div>
                                  <div style="clear:both;"></div>
                                  <div class="left_form">
                                    <%= location_form.label :hpu_id %>
                                  </div>
                                  <div class="right_form" >
                                    <% hpu_select = (@location != nil ? @location.hpu_id.to_i : '') %>
                                    <%= location_form.select(:hpu_id, "<option value=''>Select a HPU</option>" + options_from_collection_for_select(@hpus, :id, :name, hpu_select)) %>
                                  </div>
                                  <div style="clear:both;"></div>

                                <%= location_form.hidden_field :lon, :value => '' %>
                                <%= location_form.hidden_field :lat, :value => '' %>
                                <%= hidden_field_tag :postcode_error, :value => '0' %>
                                <% end %>
                          </fieldset>


                    <% end %>       

                </fieldset>

            </div>


    </div>
    <% end %>

    <div style="clear: both; margin: 10px;"></div>
    <%= observe_field(:outbreak_incidents_attributes_0_location_attributes_postcode, 
              :url => { :controller => :locations, :action => :find_lonlat },
              :on => "onchange",
              :loading => "Element.show('loader')",
              :success => "Element.hide('loader')",
              :with => "'postcode=' + encodeURIComponent($('outbreak_incidents_attributes_0_location_attributes_postcode').value)" ) %>