Ruby on rails 正在等待迁移；使用rails 4进行depot_g敏捷web开发

我需要你的帮助。
我的RubyonRails教程（Rails4的敏捷web开发，BlockG）给了我一个错误。我是Ruby新手，不知道如何修复它

来源：

class CombineItemsInCart < ActiveRecord::Migration
    def up

      Cart.all.each do |cart|
        # how many goods are in the cart?
        sums = cart.line_items.group(:product_id).sum(:quantity)
        sums.each do |product_id; quantity|
          if quantity > 1
            # remove lines
            cart.line_items.where(:product_id product_id).delete_all

            # replace with a one line
            item = cart.line_items.build(product_id: product_id)
            item.quantity = quantity
            item.save!
          end
       end
    end
  end
end

类组合ItemsInCart1
#拆线
购物车.行\u项目.其中（：产品\u id产品\u id）.全部删除
#替换为一行
item=cart.line\u items.build（产品标识：产品标识）
item.quantity=数量
物品。保存！
终止
终止
终止
终止
终止

错误是：

正在等待迁移；运行“rake db:migrate RAILS_ENV=development”到 解决这个问题

但是当我试图运行rake db:migrate时，
我在终端中收到了这个错误：

rakedb:migraterails\u ENV=development

雷克流产了！合成错误： /home/yury/Desktop/rails/depot\g/db/migrate/20170401195439\u组合购物车中的物品。rb:10： 语法错误，意外的tIDENTIFIER，应为“'）” 购物车.行\u项目.其中（：产品\u id产品\u id）.全部删除 ^/home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.0.0/lib/active\u support/dependencies.rb:228:in

require'
/home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.0.0/lib/active\u support/dependencies.rb:228:in

require中的块' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.0.0/lib/active\u support/dependencies.rb:213:in

加载依赖项'
/home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.0.0/lib/active\u support/dependencies.rb:228:in

require' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active\u record/migration.rb:718:in

load\u migration'
/home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active\u record/migration.rb:714:in

migration' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active\u record/migration.rb:708:in

disable\u ddl\u transaction'
/home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active\u record/migration.rb:1012:in

使用交易 /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active\u record/migration.rb:1004:in

ddl\u事务'
/home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active\u record/migration.rb:958:in

execute\u migration\u in\u transaction' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active\u record/migration.rb:920:in

block in migrate'
/home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active\u record/migration.rb:916:in

each' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active\u record/migration.rb:916:in

migrate'
/home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active\u record/migration.rb:764:in

up' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active\u record/migration.rb:742:in

migrate'
/home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active\u record/railties/databases.rake:42:in

in' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/rake-12.0.0/exe/rake:27:in

'
/home/yury/.rvm/gems/ruby-2.0.0-p648/bin/ruby\u可执行文件挂钩：15:in

eval' /home/yury/.rvm/gems/ruby-2.0.0-p648/bin/ruby\u可执行文件挂钩：15:in `'Tasks:TOP=>db:migrate（通过使用 --跟踪）

系统：Ubuntu 16.04 64位。 我检查了几次代码，它与书中的代码相同

有谁能帮我说说我做错了什么？我怎样才能修好它？ 谢谢

正如它所说的“

语法错误，意外的提示符，应为“'）”

“然后，代码语法中有一个输入错误，并且在

总和中。每个
块，都要更改

sums.each do |product_id; quantity|

为了

在您的
if
语句中

cart.line_items.where(:product_id product_id)

对此

cart.line_items.where(product_id: product_id)

检查手册中的原始代码：

# rails40/depot_g/db/migrate/20121130000005_combine_items_in_cart.rb
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

# rails40/depot_g/db/migrate/20121130000005_combine_items_in_cart.rb
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