cant add to cart rails 5 - ruby-on-rails

Question

my rails version is 5.0.5, i am currently developing an online store. i am following the steps on Agile web development (rails 5). i have followed the steps accordingly, i can create new products, edit products,and delete products, i am stuck at the stage where i am to add a product to cart(the "Add to cart" button shows) when i click "Add to cart" it gives me an error{cant find product with id}..........this is the error guys.
ruby 2.4.1p111 (2017-03-22 revision 58053) [i386-mingw32]
C:\Users\COMPUTER>cd desktop
C:\Users\COMPUTER\Desktop>cd trial
C:\Users\COMPUTER\Desktop\trial>cd depot
C:\Users\COMPUTER\Desktop\trial\depot>rails s
=> Booting Puma
=> Rails 5.0.5 application starting in development on http://localhost:3000
=> Run `rails server -h` for more startup options
*** SIGUSR2 not implemented, signal based restart unavailable!
*** SIGUSR1 not implemented, signal based restart unavailable!
*** SIGHUP not implemented, signal based logs reopening unavailable!
Puma starting in single mode...
* Version 3.10.0 (ruby 2.4.1-p111), codename: Russell's Teapot
* Min threads: 5, max threads: 5
* Environment: development
* Listening on tcp://0.0.0.0:3000
Use Ctrl-C to stop
Started GET "/" for 127.0.0.1 at 2017-10-22 17:44:40 +0100
ActiveRecord::SchemaMigration Load (0.0ms) SELECT "schema_migrations".* FROM "schema_migrations"
Processing by StoreController#index as HTML
Rendering store/index.html.erb within layouts/application
Product Load (4.0ms) SELECT "products".* FROM "products" ORDER BY "products"."title" ASC
Rendered store/index.html.erb within layouts/application (620.0ms)
Completed 200 OK in 1888ms (Views: 1385.1ms | ActiveRecord: 20.0ms)
Started POST "/line_items" for 127.0.0.1 at 2017-10-22 17:46:14 +0100
Processing by LineItemsController#create as HTML
Parameters: {"authenticity_token"=>"tysgjA3w3dfMA1ACBRWeigDDnDM9WDiwBDKotUwmXVVxVy0+msnR4gmkB3QV8qU8dKdLdnb5yEOS5FmdUs7LyQ=="}
Cart Load (4.0ms) SELECT "carts".* FROM "carts" WHERE "carts"."id" = ? LIMIT ? [["id", nil], ["LIMIT", 1]]
(4.0ms) begin transaction
SQL (48.0ms) INSERT INTO "carts" ("created_at", "updated_at") VALUES (?, ?) [["created_at", "2017-10-22 16:46:15.531901"], ["updated_at", "2017-10-22 16:46:15.531901"]]
(108.0ms) commit transaction
Product Load (4.0ms) SELECT "products".* FROM "products" WHERE "products"."id" = ? LIMIT ? [["id", nil], ["LIMIT", 1]]
Completed 404 Not Found in 644ms (ActiveRecord: 180.0ms)
ActiveRecord::RecordNotFound (Couldn't find Product with 'id'=):
app/controllers/line_items_controller.rb:29:in `create'
Rendering C:/Ruby24/lib/ruby/gems/2.4.0/gems/actionpack-5.0.5/lib/action_dispatch/middleware/templates/rescues/diagnostics.html.erb within rescues/layout
Rendering C:/Ruby24/lib/ruby/gems/2.4.0/gems/actionpack-5.0.5/lib/action_dispatch/middleware/templates/rescues/_source.html.erb
Rendered C:/Ruby24/lib/ruby/gems/2.4.0/gems/actionpack-5.0.5/lib/action_dispatch/middleware/templates/rescues/_source.html.erb (52.0ms)
Rendering C:/Ruby24/lib/ruby/gems/2.4.0/gems/actionpack-5.0.5/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb
Rendered C:/Ruby24/lib/ruby/gems/2.4.0/gems/actionpack-5.0.5/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb (24.0ms)
Rendering C:/Ruby24/lib/ruby/gems/2.4.0/gems/actionpack-5.0.5/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb
Rendered C:/Ruby24/lib/ruby/gems/2.4.0/gems/actionpack-5.0.5/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb (16.0ms)
Rendered C:/Ruby24/lib/ruby/gems/2.4.0/gems/actionpack-5.0.5/lib/action_dispatch/middleware/templates/rescues/diagnostics.html.erb within rescues/layout (8928.0ms)
also below is the store(the default homepage that shows the products) view file.....
<p id="notice"><%= notice %></p>
<h1>Your Pragmatic Catalog</h1>
<% cache #products do %>
<% #products.each do |product| %>
<% cache #product do %>
<div class="entry">
<h3><%= product.title %></h3>
<%= image_tag(product.image_url) %>
<%= sanitize(product.description) %>
<div class="price_line">
<span class="price"><%= number_to_currency (product.price) %></span>
<%= button_to 'Add to Cart' , line_items_path %>
</div>
</div>
<% end %>
<% end %>
<% end %>
als below is the routes......
Rails.application.routes.draw do
resources :line_items
resources :carts
root 'store#index', as: 'store_index'
resources :products
# For details on the DSL available within this file, see http://guides.rubyonrails.org/routing.html
end
and below is the products model ......
class Product < ApplicationRecord
validates :title, :description, :image_url, presence: true
validates :price, numericality: {greater_than_or_equal_to: 0.01}
validates :title, uniqueness: true
validates :image_url, allow_blank: true, format: {
with: %r{\.(gif|jpg|png)\Z}i,
message: 'must be a URL for GIF, JPG or PNG image.'
}
has_many :line_items
before_destroy :ensure_not_referenced_by_any_line_item
#...
private
# ensure that there are no line items referencing this product
def ensure_not_referenced_by_any_line_item
unless line_items.empty?
errors.add(:base, 'Line Items present')
throw :abort
end
end
end
below is the carts model....
class Cart < ApplicationRecord
has_many :line_items, dependent: :destroy
end
def add_product (lineitem, product_id)
current_item = line_items.find_by(product_id: product.id)
if current_item
current_item.quantity += 1
else
current_item = line_items.build(product_id: product.id)
end
current_item
end
line items model....
class LineItem < ApplicationRecord
belongs_to :product
belongs_to :cart
end
application_record.rb........
class ApplicationRecord < ActiveRecord::Base
self.abstract_class = true
end
carts controller....
class CartsController < ApplicationController
before_action :set_cart, only: [:show, :edit, :update, :destroy]
# GET /carts
# GET /carts.json
def index
#carts = Cart.all
end
# GET /carts/1
# GET /carts/1.json
def show
end
# GET /carts/new
def new
#cart = Cart.new
end
# GET /carts/1/edit
def edit
end
# POST /carts
# POST /carts.json
def create
#cart = Cart.new(cart_params)
respond_to do |format|
if #cart.save
format.html { redirect_to #cart, notice: 'Cart was successfully created.' }
format.json { render :show, status: :created, location: #cart }
else
format.html { render :new }
format.json { render json: #cart.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /carts/1
# PATCH/PUT /carts/1.json
def update
respond_to do |format|
if #cart.update(cart_params)
format.html { redirect_to #cart, notice: 'Cart was successfully updated.' }
format.json { render :show, status: :ok, location: #cart }
else
format.html { render :edit }
format.json { render json: #cart.errors, status: :unprocessable_entity }
end
end
end
# DELETE /carts/1
# DELETE /carts/1.json
def destroy
#cart.destroy
respond_to do |format|
format.html { redirect_to carts_url, notice: 'Cart was successfully destroyed.' }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_cart
#cart = Cart.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def cart_params
params.fetch(:cart, {})
end
end
application controller.....
class ApplicationController < ActionController::Base
protect_from_forgery with: :exception
end
line items controller....
class LineItemsController < ApplicationController
include CurrentCart
before_action :set_cart, only: [:create]
before_action :set_line_item, only: [:show, :edit, :update, :destroy]
# GET /line_items
# GET /line_items.json
def index
#line_items = LineItem.all
end
# GET /line_items/1
# GET /line_items/1.json
def show
end
# GET /line_items/new
def new
#line_item = LineItem.new
end
# GET /line_items/1/edit
def edit
end
# POST /line_items
# POST /line_items.json
def create
product = Product.find (params[:product_id])
#line_item = #cart.line_items.build(product: product)
respond_to do |format|
if #line_item.save
format.html { redirect_to #line_item.cart, notice: 'Line item was successfully created.' }
format.json { render :show, status: :created, location: #line_item }
else
format.html { render :new }
format.json { render json: #line_item.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /line_items/1
# PATCH/PUT /line_items/1.json
def update
respond_to do |format|
if #line_item.update(line_item_params)
format.html { redirect_to #line_item, notice: 'Line item was successfully updated.' }
format.json { render :show, status: :ok, location: #line_item }
else
format.html { render :edit }
format.json { render json: #line_item.errors, status: :unprocessable_entity }
end
end
end
# DELETE /line_items/1
# DELETE /line_items/1.json
def destroy
#line_item.destroy
respond_to do |format|
format.html { redirect_to line_items_url, notice: 'Line item was successfully destroyed.' }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_line_item
#line_item = LineItem.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def line_item_params
params.require(:line_item).permit(:product_id, :cart_id)
end
end
products controller...
class ProductsController < ApplicationController
before_action :set_product, only: [:show, :edit, :update, :destroy]
# GET /products
# GET /products.json
def index
#products = Product.all
end
# GET /products/1
# GET /products/1.json
def show
end
# GET /products/new
def new
#product = Product.new
end
# GET /products/1/edit
def edit
end
# POST /products
# POST /products.json
def create
#product = Product.new(product_params)
respond_to do |format|
if #product.save
format.html { redirect_to #product, notice: 'Product was successfully created.' }
format.json { render :show, status: :created, location: #product }
else
format.html { render :new }
format.json { render json: #product.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /products/1
# PATCH/PUT /products/1.json
def update
respond_to do |format|
if #product.update(product_params)
format.html { redirect_to #product, notice: 'Product was successfully updated.' }
format.json { render :show, status: :ok, location: #product }
else
format.html { render :edit }
format.json { render json: #product.errors, status: :unprocessable_entity }
end
end
end
# DELETE /products/1
# DELETE /products/1.json
def destroy
#product.destroy
respond_to do |format|
format.html { redirect_to products_url, notice: 'Product was successfully destroyed.' }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_product
#product = Product.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def product_params
params.require(:product).permit(:title, :description, :image_url, :price)
end
end
store controller.....
class StoreController < ApplicationController
def index
#products = Product.order(:title)
end
end

Answer 1

Your error is ActiveRecord::RecordNotFound (Couldn't find Product with 'id'=):. This means that the controller doesn't know which product you want to add to the cart. This would be done by adding a product_id to the params of your POST.
In your view:
<%= button_to 'Add to Cart' , line_items_path %>
The line_items_path probably isn't correct. You probably want line_item_path(product_id: product.id). This will add the product's ID to the request and make it available when the controller tries to find the record here:
product = Product.find (params[:product_id])

Answer 2

In the view you have to send the correct product_id as suggested by Daniel Westendorf
<%= button_to 'Add to Cart' , line_items_path(product_id: product.id) %>
So, in this way when you create a new LineItem in new method of LinesItemController, you have it params
def new
#line_item = LineItem.new(params[:product_id])
end
For using the debug mode you can use byebug and you can use this step_by_step installation guide.
pry is another alternative.