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

Question

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                          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?

Pasted Pasted · Accepted Answer · 2010-11-26T11:37:03

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

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

2 Answers