灵活的网页开发与轨道4
我需要你的帮助。
我的Ruby on Rails教程（带rails 4的敏捷web开发，块g）给了我一个错误。 我是Ruby新手，不知道如何解决这个问题。
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
错误是：
迁移正在进行中; 运行'rake db：migrate RAILS_ENV = development'来解决这个问题。
但是当我试图运行rake db：migrate时 ，
我在终端收到这个错误：
rake db：migrate RAILS_ENV =开发
耙子中止了！ SyntaxError：/home/yury/Desktop/rails/depot_g/db/migrate/20170401195439_combine_items_in_cart.rb:10：语法错误，意外的tIDENTIFIER，期待'）'cart.line_items.where（：product_id product_id）.delete_all ^ / home / yury /.rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:228:in require' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:228:in block中require' require' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:228:in 4.0。 0 / lib / active_support / dependencies.rb：213：in load_dependency' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:228:in / load_dependency' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:228:in / load_dependency' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:228:in / load_dependency' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:228:in / load_dependency' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:228:in / load_dependency' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:228:in / load_dependency' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:228:in /lib/active_support/dependencies.rb: load_dependency' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:228:in require'/home/ load_migration' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active_record/migration.rb:714:in gems/ load_migration' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active_record/migration.rb:714:in gems/ load_migration' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active_record/migration.rb:714:in active_record/ load_migration' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active_record/migration.rb:714:in load_dependency' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:228:in load_migration' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active_record/migration.rb:714:in migration'/home/yury/.rvm/gems/ruby-2.0.0-p648/宝石/了activerecord-4.0.0 / LIB / active_record / migration.rb：70 8：在disable_ddl_transaction' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active_record/migration.rb:1012:in : disable_ddl_transaction' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active_record/migration.rb:1012:in :in use_transaction？' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active_record/migration.rb:1004:in ddl_transaction' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active_record/migration.rb:958:in yury/ ddl_transaction' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active_record/migration.rb:958:in execute_migration_in_transaction' ddl_transaction' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active_record/migration.rb:958:in 4.0.0 / lib / active_record / migration.rb：920： block in migrate' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active_record/migration.rb:916:in中的block in migrate' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active_record/migration.rb:916:in每个'/home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active_record/migration.rb:916:in migrate' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active_record/migration.rb:764:in '/home/yury/.rvm/gems/ruby-2.0。 0-p648 / gems / activerecord-4.0.0 / lib / active_record / migration.rb：742：in migrate' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active_record/railties/databases.rake:42:in /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0 migrate' /home/yury/.rvm/gems/ruby-2.0.0-p648/gems/activerecord-4.0.0/lib/active_record/railties/databases.rake:42:in levels）in'/home/yury/.rvm/gems/ruby-2.0.0-p648/gems/rake-12.0.0/exe/rake ：27：在<top (required)>' /home/yury/.rvm/gems/ruby-2.0.0-p648/bin/ruby_executable_hooks:15:in <top (required)>' /home/yury/.rvm/gems/ruby-2.0.0-p648/bin/ruby_executable_hooks:15:in yury/.rvm/gems/ruby-2.0.0-p648/bin/ruby_executable_hooks:15: <top (required)>' /home/yury/.rvm/gems/ruby-2.0.0-p648/bin/ruby_executable_hooks:15:in eval'/home/yury/.rvm/gems/ruby-2.0.0-p648/bin / ruby_executable_hooks：15：在''任务：TOP => db：migrate（通过使用--trace运行任务来查看完整跟踪）
系统：Ubuntu 16.04 64位。 我检查了几次代码，它和本书中的一样。
那么有人能帮助我，并告诉我做错了什么吗？ 我该如何解决它？ 谢谢！
正如它所说的“ syntax error, unexpected tIDENTIFIER, expecting ')' ”，那么在你的代码语法中有一个错字，并且在你的sums.each块中，改变
sums.each do |product_id; quantity|
对于
sums.each do |product_id, quantity|
而在你if从这句话
cart.line_items.where(:product_id product_id)
对此
cart.line_items.where(product_id: product_id)
检查书中的原始代码：
# 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