Question

I have a field that creates a comment (named pcomment). I am trying to get it to automatically add the user_id to the pcomment in the pcomment table like it adds the purchase_id automatically. I am not sure why the purchase_id is being recorded in the database but the user_id remains blank for each pcomment. Here is the form for the pcomment.

<%= form_for([purchase, purchase.pcomments.build], :html => { :id => "blah_form" }) do |f| %>

    <div class="field">
      <h4>What deal are you offering?</h4>
      <%= f.text_field :body %>
    </div>

  <% end %>

It may be that I have to add some hidden_field, but I don’t think so. I am using http://ruby.railstutorial.org/book/ruby-on-rails-tutorial#cha-user_microposts as resource and in that the microposts dont have any hidden_field. Instead, the user_id is indexed and it automatically is created upon the creation of a micropost (based on who is signed in at the time). This part is working for me too, adding to my rational that indexing user_id on the pcomments table is enough to automatically generate it. Here is my schema.rb file so that you can see the current state of my database.

   ActiveRecord::Schema.define(:version => 20121011085147) do

  create_table "pcomments", :force => true do |t|
    t.string   "body"
    t.integer  "purchase_id"
    t.integer  "user_id"
    t.datetime "created_at",  :null => false
    t.datetime "updated_at",  :null => false
  end

  add_index "pcomments", ["purchase_id"], :name => "index_pcomments_on_purchase_id"
  add_index "pcomments", ["user_id"], :name => "index_pcomments_on_user_id"

  create_table "purchases", :force => true do |t|
    t.string   "content"
    t.integer  "user_id"
    t.datetime "created_at", :null => false
    t.datetime "updated_at", :null => false
  end

  add_index "purchases", ["user_id", "created_at"], :name => "index_purchases_on_user_id_and_created_at"

  create_table "sales", :force => true do |t|
    t.string   "content"
    t.integer  "user_id"
    t.datetime "created_at", :null => false
    t.datetime "updated_at", :null => false
  end

  add_index "sales", ["user_id", "created_at"], :name => "index_sales_on_user_id_and_created_at"

  create_table "scomments", :force => true do |t|
    t.string   "body"
    t.integer  "sale_id"
    t.integer  "user_id"
    t.datetime "created_at", :null => false
    t.datetime "updated_at", :null => false
  end

  add_index "scomments", ["sale_id"], :name => "index_scomments_on_sale_id"
  add_index "scomments", ["user_id"], :name => "index_scomments_on_user_id"

  create_table "users", :force => true do |t|
    t.string   "name"
    t.string   "email"
    t.datetime "created_at",                         :null => false
    t.datetime "updated_at",                         :null => false
    t.string   "password_digest"
    t.string   "remember_token"
    t.boolean  "admin",           :default => false
  end

  add_index "users", ["email"], :name => "index_users_on_email", :unique => true
  add_index "users", ["remember_token"], :name => "index_users_on_remember_token"

end

and the reason I know its not working is that I check in the database and the pcomment is successfully created with all columns filled in including purchase_id but the user_id is still blank. also, the user has_many pcomments and has_many purchases. The purchase has_many pcomments and belongs_to user. The pcomment belongs_to user and belong_to purchase.

also, here is the pcomments_controller.rb

    class PcommentsController < ApplicationController
  before_filter :signed_in_user
  def create
    @purchase = Purchase.find(params[:purchase_id])
    @pcomment = @purchase.pcomments.build(params[:pcomment], :user_id => @purchase.user_id)

    @pcomment.purchase = @purchase

    if @pcomment.save
       flash[:success] = "Offer submited!"
       redirect_to :back
    else
      render 'shared/_pcomment_form'
    end
  end

  def new
    @pcomment=purchase.pcomments.new
  end


end

      def new
        @pcomment=purchase.pcomments.new(:user_id => purchase.user_id)
      end


    end

Answer 1

purchase.pcomments.build builds empty Pcomment object just with purchase_id filled from purchase. To assign also user_id pass the hash with attribute:

purchase.pcomments.build(:user_id => purchase.user_id)