Nested attributes fail in rails 5, but works in rails 4

Question

I have an exercise called "BillApp" basically it's a Bill that have some products, and i should could make bills, calculate IVA, etc.

I have the next schema:

create_table "bill_items", force: :cascade do |t|
    t.integer  "amount"
    t.integer  "product_id"
    t.integer  "bill_id"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.index ["bill_id"], name: "index_bill_items_on_bill_id"
    t.index ["product_id"], name: "index_bill_items_on_product_id"
  end

  create_table "bills", force: :cascade do |t|
    t.string   "user_name"
    t.string   "dni"
    t.date     "expiration"
    t.float    "sub_total"
    t.float    "grand_total"
    t.datetime "created_at",  null: false
    t.datetime "updated_at",  null: false
  end

  create_table "products", force: :cascade do |t|
    t.string   "name"
    t.string   "description"
    t.float    "price"
    t.datetime "created_at",  null: false
    t.datetime "updated_at",  null: false
  end

Bill model:

class Bill < ApplicationRecord
  has_many :bill_items
  has_many :products, through: :bill_items
  accepts_nested_attributes_for :bill_items
end

BillItem model:

class BillItem < ApplicationRecord
  belongs_to :product
  belongs_to :bill
end

Product model:

class Product < ApplicationRecord
  has_many :bill_items
  has_many :bills, through: :bill_items
end

The ProductsController is a normal one, generated by scaffold, it doesn't matter.

BillsController:

class BillsController < ApplicationController
  before_action :set_bill, only: [:show, :update, :destroy, :edit]

  def new
    @bill = Bill.new
    @bill.bill_items.build
  end

  def create
    @bill = Bill.new(bill_params)
    byebug
    @bill.save
  end

  private
    def set_bill
      @bill = Bill.find(params[:id])
    end

    def bill_params
      params.require(:bill).permit(:user_name, :dni, { bill_items_attributes: [:product_id, :amount, :bill_id] })
    end
end

And finally the Bill new view:

<%= form_for(@bill) do |f| %>
  <div>
    <%= f.label :user_name %>
    <%= f.text_field :user_name %>
  </div>
  <div>
    <%= f.label :dni %>
    <%= f.text_field :dni %>
  </div>

  <%= f.fields_for :bill_items do |fp| %>
    <div>
      <%= fp.label :product %>
      <%= fp.collection_select :product_id, Product.all, :id, :name %>
    </div>
    <div>
      <%= fp.label :amount %>
      <%= fp.number_field :amount %>
    </div>
  <% end %>

  <%= f.submit %></div>
<% end %>

The problem is very specific, in rails 5 when it try to call @bill.save it fails and in the errors it shows:

#<ActiveModel::Errors:0x007fd9ea61ed58 @base=#<Bill id: nil, user_name: "asd", dni: "asd", expiration: nil, sub_total: nil, grand_total: nil, created_at: nil, updated_at: nil>, @messages={:"bill_items.bill"=>["must exist"]}, @details={"bill_items.bill"=>[{:error=>:blank}]}>

But it works perfectly in Rails 4.2.6. The entire project folder is here: https://github.com/TheSwash/bill_app currentrly in the branch feature/bills_controller

Somebody have an idea about what's happening?

Answer 1

the problem it's the bill_items validation

In rails 5 the belongs_to association required by default

http://blog.bigbinary.com/2016/02/15/rails-5-makes-belong-to-association-required-by-default.html