Building a shopping cart with rails

New to rails. I have seen several tutorials online, but am unable to get a simple shopping cart functionality. Following is my code and the error i am getting.

class CartsController < ApplicationController

def add
    @current_cart = @cart
    @current_cart = @current_cart.products.new(product_params)
    @current_cart.save
    session[:current_cart_id] = @current_cart.id

    redirect_to :back
  end



def delete
  end

  def show
    #@cart = initialize_cart.cart
  end

  private

  def product_params
    params.permit(:id)
  end

end

Application Controller

class ApplicationController < ActionController::Base
  protect_from_forgery with: :exception

  before_filter :initialize_cart

  def initialize_cart
    if session[:cart]
      @cart = Cart.find(session[:cart])
    else
      @cart = Cart.create
      session[:cart] = @cart.id
    end
  end

end

Link to Add to Cart Button

<%= link_to "Add to Cart", :controller => "carts", :action => "add", :id => @product.id, :class => "btn bg-turquoise"%>

routes.rb

get 'carts/add/:id', to: 'carts#add'

get 'carts/delete'

get 'carts/show', to: 'carts#show', as: 'showcart'

Error:

ActiveModel::UnknownAttributeError in CartsController#add

unknown attribute 'cart_id' for Product.

Extracted source (around line #5):

3 def add
4   @current_cart = @cart
**5     @current_cart = @current_cart.products.new(product_params)**
6   @current_cart.save
7   session[:current_cart_id] = @current_cart.id

Any help or guidance is appreciated. Thanks!