Smarter Cart--with quantities

app/controllers/line_items_controller.rb

@@ -42,8 +42,9 @@ def edit
   def create
     @cart = current_cart
     product = Product.find(params[:product_id])
-    @line_item = @cart.line_items.build(product_id: product)
-    @line_item.product = product
+    #@line_item = @cart.line_items.build(product_id: product)
+    @line_item = @cart.add_product(product.id)
+    #@line_item = @cart.add_product(product_id: product.id)
 
     respond_to do |format|
       if @line_item.save

app/models/cart.rb

@@ -2,5 +2,15 @@ class Cart < ActiveRecord::Base
   # attr_accessible :title, :body
 
   has_many :line_items, dependent: :destroy
+
+  def add_product(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
 end
 

app/models/line_item.rb

@@ -1,7 +1,7 @@
 class LineItem < ActiveRecord::Base
   #attr_accessible :cart_id, :product_id
 
-  attr_accessible :product_id, :id, :cart_id, :created_at, :updated_at
+  attr_accessible :id, :cart_id, :product_id, :created_at, :updated_at, :product
 
   belongs_to :product
   belongs_to :cart

app/views/carts/show.html.erb

@@ -5,7 +5,7 @@
 <h2>Your Pragmatic Cart</h2>
 <ul>
   <% @cart.line_items.each do |item| %>
-    <li><%= item.product.title %></li>
+    <li><%= item.quantity %> &times; <%= item.product.title %></li>
   <% end %>
 </ul>
 

db/migrate/20120822003344_add_quantity_to_line_items.rb

@@ -0,0 +1,6 @@
+class AddQuantityToLineItems < ActiveRecord::Migration
+  def change
+    add_column :line_items, :quantity, :integer, default: 1
+  end
+end
+

db/migrate/20120822005458_combine_items_in_cart.rb

@@ -0,0 +1,37 @@
+class CombineItemsInCart < ActiveRecord::Migration
+
+  def up
+    # replace multiple items for a single product in a cart with a single item
+    Cart.all.each do |cart|
+      # count the number of each product in the cart
+      sums = cart.line_items.group(:product_id).sum(:quantity)
+
+      sums.each do |product_id, quantity|
+        if quantity > 1
+          # remove individual items
+          cart.line_items.where(product_id: product_id).delete_all
+
+          # replace with a single item
+          item = cart.line_items.build(product_id: product_id)
+          item.quantity = quantity
+          item.save!
+        end
+      end
+    end
+  end
+
+def down
+    # split items with quantity>1 into multiple items
+    LineItem.where("quantity>1").each do |line_item|
+      # add individual items
+      line_item.quantity.times do
+        LineItem.create cart_id: line_item.cart_id,
+          product_id: line_item.product_id
+      end
+
+      # remove original item
+      line_item.destroy
+    end
+  end
+end
+

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended to check this file into your version control system.
 
-ActiveRecord::Schema.define(:version => 20120822001052) do
+ActiveRecord::Schema.define(:version => 20120822005458) do
 
   create_table "carts", :force => true do |t|
     t.datetime "created_at", :null => false
@@ -21,8 +21,9 @@
   create_table "line_items", :force => true do |t|
     t.integer  "product_id"
     t.integer  "cart_id"
-    t.datetime "created_at", :null => false
-    t.datetime "updated_at", :null => false
+    t.datetime "created_at",                :null => false
+    t.datetime "updated_at",                :null => false
+    t.integer  "quantity",   :default => 1
   end
 
   create_table "products", :force => true do |t|