Nested forms not storing data into database in rails 4 - ruby-on-rails

Question

I have a vendor model, a product model, and a vendor_product model. In my vendors form, I have used nested form to create vendor_products with attributes as vendor_id, product_id and copies.On creating a new vendor, it also creates a vendor_product. But for some reason, it does not stores the vendor_id and product_id in vendor_products table but only stores the copies
My associations are as follows
A vendor ->
has_many :vendor_products
has_many :products, through: :vendor_products
A product ->
has_many :vendor_products
has_many :vendors, through: :vendor_products
A vendor_product
belongs_to :vendor
belongs_to :product
Vendor.rb
class Vendor < ActiveRecord::Base
has_many :vendor_products
has_many :products, through: :vendor_products
accepts_nested_attributes_for :vendor_products, :products,
:allow_destroy => true
end
My vendors/_form.html.erb
<%= form_for(#vendor) do |f| %>
<% if #vendor.errors.any? %>
<div id="error_explanation">
<h2><%= pluralize(#vendor.errors.count, "error") %> prohibited this
vendor from being saved:</h2>
<ul>
<% #vendor.errors.full_messages.each do |message| %>
<li><%= message %></li>
<% end %>
</ul>
</div>
<% end %>
<div class="field">
<%= f.label :name %><br>
<%= f.text_field :name %>
</div>
:
:
:
<%= f.fields_for :vendor_products do |vproducts| %>
<div class="field">
<%= vproducts.label :product %><br>
<%= collection_select(:product, :product_ids, Product.all, :id,
:product_name,
{:prompt => 'Please select', :multiple => true }) %>
</div>
<div class="field">
<%= vproducts.label :copies %><br>
<%= vproducts.number_field :copies %>
</div>
<% end %>
<div class="actions">
<%= f.submit %>
</div>
<% end %>
My vendors_controller.rb
class VendorsController < ApplicationController
before_action :set_vendor, only: [:show, :edit, :update, :destroy]
respond_to :json
def index
#vendors = Vendor.all.limit(20)
end
def show
end
def new
#vendor = Vendor.new
#vendor.products.build
#vendor.vendor_products.build
end
def edit
end
def create
#vendor = Vendor.new(vendor_params)
respond_to do |format|
if #vendor.save
format.html { redirect_to #vendor, notice: 'Vendor was successfully
created.' }
format.json { render :show, status: :created, location: #vendor }
else
format.html { render :new }
format.json { render json: #vendor.errors, status:
:unprocessable_entity }
end
end
end
def update
respond_to do |format|
if #vendor.update(vendor_params)
format.html { redirect_to #vendor, notice: 'Vendor was successfully
updated.' }
format.json { render :show, status: :ok, location: #vendor }
else
format.html { render :edit }
format.json { render json: #vendor.errors, status:
:unprocessable_entity }
end
end
end
private
def set_vendor
#vendor = Vendor.find(params[:id])
end
def vendor_params
params.require(:vendor).permit(:name, :email, :phone_no, :addressline1,
:addressline2, :landmark,
:city, :state, :country, :pincode, :latitude, :longitude, :status,
product_attributes: [:product_id, :product_name, :price ],
vendor_products: [:vendor_product_id, :vendor_id, :product_id,
:copies])
end
end
Now a vendor and VendorProduct is created but my vendor_product looks lik this
{"id":3,
"vendor_id":null,
"product_id":null,
"copies":4,
}
Can any one point out how to fix this. What am I doing wrong. Please bear in mind that I am a rails newbie.

Answer 1

change once vendor_products to vendor_products_attributes and look
In your view
<%= collection_select(:product, :product_ids, Product.all, :id,
:product_name,
{:prompt => 'Please select', :multiple => true }) %>
replace with
<%= vproducts.select :product_id, options_from_collection_for_select(Product.all, "id", "name"), prompt: "Select something" %>

Answer 2

Change this line:
<%= collection_select(:product, :product_ids, Product.all, :id,
:product_name,
{:prompt => 'Please select', :multiple => true }) %>
</div>
to
<%= collection_select(:product, :product_id, Product.all, :id,
:product_name,
{:prompt => 'Please select', :multiple => true }) %>
</div>