Adding Cart items Ruby on Rails - ruby-on-rails

Question

I am developing a very basic shopping cart and the issue I am having is that if I add more than one of the same product to my shopping cart I am not seeing the quantity increase and am instead just seeing multiple versions of the item.
For example I see:
1 x green light = £15
1 x green light = £15
rather than seeing:
2 x green light = £30
How can I make it so that my shopping cart will check for multiple versions in the cart and then add them together?
Currently I have:
Application Controller
def current_cart
if session[:cart_id]
#current_cart ||= Cart.find(session[:cart_id])
end
if session[:cart_id].nil?
#current_cart = Cart.create!
session[:cart_id] = #current_cart.id
end
#current_cart
end
Cart Controller
def show
#cart = current_cart
end
Cart Model
has_many :items
def total_price
items.to_a.sum(&:full_price)
end
Cart View
<table id="line_items">
<tr>
<th>Product</th>
<th>Qty</th>
<th class="price">Unit Price</th>
<th class="price">Full Price</th>
</tr>
<% for item in #cart.items %>
<tr class="<%= cycle :odd, :even %>">
<td><%=h item.product.name %></td>
<td class="qty"><%= item.quantity %></td>
<td class="price"><%= gbp(item.unit_price) %></td>
<td class="price"><%= gbp(item.full_price) %></td>
</tr>
<% end %>
<tr>
<td class="total price" colspan="4">
Total: <%= gbp(#cart.total_price) %>
</td>
</tr>
</table>
FURTHER INFORMATION
Products#Index
<%= link_to "Add to Cart", line_items_path(:product_id => product), :method => :post %>
Any advice people can offer would be much appreciated. Thanks!
New Setup - Causing Error Uninitialised Constant CartController
Routes.rb
Checkout::Application.routes.draw do
ActiveAdmin.routes(self)
devise_for :admin_users, ActiveAdmin::Devise.config
post '/add_to_cart/:product_id' => 'cart#add_to_cart', :as => 'add_to_cart'
resources :carts
resources :products
resources :items
root :to => 'products#index'
end
Carts Controller
class CartsController < ApplicationController
def show
#cart = current_cart
end
def add_to_cart
current_cart.add_item(params[:product_id])
redirect_to carts_path(current_cart.id)
end
end
Carts Model
class Cart < ActiveRecord::Base
has_many :items
def add_item(product_id)
item = items.where('product_id = ?', product_id).first
if item
# increase the quantity of product in cart
item.quantity + 1
save
else
# product does not exist in cart
product = Product.find(product_id)
items << product
end
save
end
def total_price
items.to_a.sum(&:full_price)
end
end
Product#Index
<table class="jobs">
<thead>
<tr>
<th scope="col" id="name">Product Code</th>
<th scope="col" id="company">Name</th>
<th scope="col" id="company">Price</th>
<th scope="col" id="company">Action</th>
</tr>
</thead>
<tbody>
<% #product.each do |product| %>
<tr>
<td><%= product.product_code %></td>
<td><%= product.name %></td>
<td><%= gbp(product.price) %></td>
<td><%= button_to "Add to Cart", add_to_cart_path(:product_id => product), :method => :post %></td>
</tr>
<% end %>
</tbody>
</table>

Answer 1

In your Cart model, create a method called
def add_item(product_id)
item = items.where('product_id = ?', product_id).first
if item
# increase the quantity of product in cart
item.quantity + 1
save
else
# product does not exist in cart
cart.items << Item.new(product_id: product_id, quantity: 1)
end
save
end
In routes.rb,
post '/add_to_cart/:product_id' => 'cart#add_to_cart', :as => 'add_to_cart'
Change your Add to Cart route to a call add_to_cart method in the Cart controller.
def add_to_cart
current_cart.add_item(params[:product_id])
# redirect to shopping cart or whereever
end
This should give you the idea of what you are wanting to accomplish.