Playtime Iteration E.

app/models/cart.rb

@@ -8,6 +8,8 @@ class Cart < ApplicationRecord
     else
       current_item = line_items.build(product_id: product.id)
     end
+    # QUESTION: What happens if the price change in between to additions?
+    current_item.price = product.price
     current_item
   end
 

db/migrate/20161116182902_add_price_to_line_items.rb

@@ -0,0 +1,5 @@
+class AddPriceToLineItems < ActiveRecord::Migration[5.0]
+  def change
+    add_column :line_items, :price, :decimal, precision: 8, scale: 2
+  end
+end

db/migrate/20161116183040_fill_price_in_line_items.rb

@@ -0,0 +1,12 @@
+class FillPriceInLineItems < ActiveRecord::Migration[5.0]
+  def up
+    LineItem.all.each do |item|
+      product = Product.find(item.product_id)
+      item.price = product.price
+      item.save!
+    end
+  end
+
+  def down
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20161116161423) do
+ActiveRecord::Schema.define(version: 20161116183040) do
 
   create_table "carts", force: :cascade do |t|
     t.datetime "created_at", null: false
@@ -20,10 +20,11 @@ ActiveRecord::Schema.define(version: 20161116161423) do
   create_table "line_items", force: :cascade do |t|
     t.integer  "product_id"
     t.integer  "cart_id"
-    t.datetime "created_at",             null: false
-    t.datetime "updated_at",             null: false
-    t.integer  "quantity",   default: 1
+    t.datetime "created_at",                                     null: false
+    t.datetime "updated_at",                                     null: false
+    t.integer  "quantity",                           default: 1
     t.integer  "order_id"
+    t.decimal  "price",      precision: 8, scale: 2
     t.index ["cart_id"], name: "index_line_items_on_cart_id"
     t.index ["order_id"], name: "index_line_items_on_order_id"
     t.index ["product_id"], name: "index_line_items_on_product_id"