好的，所以我正在阅读“使用Rails进行敏捷Web开发”并开始使用软件仓库应用程序。对于那些有本书的人来说，这是第9.3章迭代D3：添加一个按钮。
在此部分之前，我们创建了一个会话来保存我们的“购物车”
class ApplicationController < ActionController::Base
protect_from_forgery
private
def current_cart
Cart.find(session[:cart_id])
rescue ActiveRecord::RecordNotFound
cart = Cart.create
session[:cart_id] = cart.id
cart
end
end
使我们创建的任何扩展ApplicationController的控制器都可以访问我们的购物车。
在本节中，我们编辑LineItemsController类的“create”函数，该函数扩展了ApplicationControler。
原始的create方法如下所示
def create
@line_item = LineItem.new(params[:line_item])
respond_to do |format|
if @line_item.save
format.html { redirect_to @line_item, notice: 'Line item was successfully created.' }
format.json { render json: @line_item, status: :created, location: @line_item }
else
format.html { render action: "new" }
format.json { render json: @line_item.errors, status: :unprocessable_entity }
end
end
end
这本书说如果这样修改。
def create
@cart = current_cart
product = Product.find(params[:product_id])
@line_item = @cart.line_items.build(product: product)
respond_to do |format|
if @line_item.save
format.html { redirect_to @line_item.cart, notice: 'Line item was successfully created.' }
format.json { render json: @line_item, status: :created, location: @line_item }
else
format.html { render action: "new" }
format.json { render json: @line_item.errors, status: :unprocessable_entity }
end
end
end
我已经对代码进行了三次检查。我从书中复制了它。不是红宝石专家，我不知道我错过了什么。它给我的错误就是这个。
ArgumentError in LineItemsController#create
wrong number of arguments (0 for 1)
Rails.root: /Users/jandrews/Projects/pragprog_ruby/depot
Application Trace | Framework Trace | Full Trace
activerecord (3.1.3) lib/active_record/relation.rb:318:in `destroy'
activerecord (3.1.3) lib/active_record/base.rb:442:in `destroy'
app/models/cart.rb:2:in `<class:Cart>'
app/models/cart.rb:1:in `<top (required)>'
activesupport (3.1.3) lib/active_support/dependencies.rb:456:in `load'
activesupport (3.1.3) lib/active_support/dependencies.rb:456:in `block in load_file'
activesupport (3.1.3) lib/active_support/dependencies.rb:640:in `new_constants_in'
activesupport (3.1.3) lib/active_support/dependencies.rb:455:in `load_file'
activesupport (3.1.3) lib/active_support/dependencies.rb:342:in `require_or_load'
activesupport (3.1.3) lib/active_support/dependencies.rb:489:in `load_missing_constant'
activesupport (3.1.3) lib/active_support/dependencies.rb:181:in `block in const_missing'
activesupport (3.1.3) lib/active_support/dependencies.rb:179:in `each'
activesupport (3.1.3) lib/active_support/dependencies.rb:179:in `const_missing'
activesupport (3.1.3) lib/active_support/dependencies.rb:501:in `load_missing_constant'
activesupport (3.1.3) lib/active_support/dependencies.rb:181:in `block in const_missing'
activesupport (3.1.3) lib/active_support/dependencies.rb:179:in `each'
activesupport (3.1.3) lib/active_support/dependencies.rb:179:in `const_missing'
app/controllers/application_controller.rb:7:in `current_cart'
app/controllers/line_items_controller.rb:43:in `create'
actionpack (3.1.3) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
actionpack (3.1.3) lib/abstract_controller/base.rb:167:in `process_action'
actionpack (3.1.3) lib/action_controller/metal/rendering.rb:10:in `process_action'
actionpack (3.1.3) lib/abstract_controller/callbacks.rb:18:in `block in process_action'
activesupport (3.1.3) lib/active_support/callbacks.rb:416:in `_run__1422100127945824718__process_action__3684163507935076470__callbacks'
activesupport (3.1.3) lib/active_support/callbacks.rb:386:in `_run_process_action_callbacks'
activesupport (3.1.3) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.1.3) lib/abstract_controller/callbacks.rb:17:in `process_action'
actionpack (3.1.3) lib/action_controller/metal/rescue.rb:17:in `process_action'
actionpack (3.1.3) lib/action_controller/metal/instrumentation.rb:30:in `block in process_action'
activesupport (3.1.3) lib/active_support/notifications.rb:53:in `block in instrument'
activesupport (3.1.3) lib/active_support/notifications/instrumenter.rb:21:in `instrument'
activesupport (3.1.3) lib/active_support/notifications.rb:53:in `instrument'
actionpack (3.1.3) lib/action_controller/metal/instrumentation.rb:29:in `process_action'
actionpack (3.1.3) lib/action_controller/metal/params_wrapper.rb:201:in `process_action'
activerecord (3.1.3) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
actionpack (3.1.3) lib/abstract_controller/base.rb:121:in `process'
actionpack (3.1.3) lib/abstract_controller/rendering.rb:45:in `process'
actionpack (3.1.3) lib/action_controller/metal.rb:193:in `dispatch'
actionpack (3.1.3) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
actionpack (3.1.3) lib/action_controller/metal.rb:236:in `block in action'
actionpack (3.1.3) lib/action_dispatch/routing/route_set.rb:65:in `call'
actionpack (3.1.3) lib/action_dispatch/routing/route_set.rb:65:in `dispatch'
actionpack (3.1.3) lib/action_dispatch/routing/route_set.rb:29:in `call'
rack-mount (0.8.3) lib/rack/mount/route_set.rb:152:in `block in call'
rack-mount (0.8.3) lib/rack/mount/code_generation.rb:96:in `block in recognize'
rack-mount (0.8.3) lib/rack/mount/code_generation.rb:75:in `optimized_each'
rack-mount (0.8.3) lib/rack/mount/code_generation.rb:95:in `recognize'
rack-mount (0.8.3) lib/rack/mount/route_set.rb:141:in `call'
actionpack (3.1.3) lib/action_dispatch/routing/route_set.rb:532:in `call'
actionpack (3.1.3) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
rack (1.3.6) lib/rack/etag.rb:23:in `call'
rack (1.3.6) lib/rack/conditionalget.rb:35:in `call'
actionpack (3.1.3) lib/action_dispatch/middleware/head.rb:14:in `call'
actionpack (3.1.3) lib/action_dispatch/middleware/params_parser.rb:21:in `call'
actionpack (3.1.3) lib/action_dispatch/middleware/flash.rb:247:in `call'
rack (1.3.6) lib/rack/session/abstract/id.rb:195:in `context'
rack (1.3.6) lib/rack/session/abstract/id.rb:190:in `call'
actionpack (3.1.3) lib/action_dispatch/middleware/cookies.rb:331:in `call'
activerecord (3.1.3) lib/active_record/query_cache.rb:64:in `call'
activerecord (3.1.3) lib/active_record/connection_adapters/abstract/connection_pool.rb:477:in `call'
actionpack (3.1.3) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
activesupport (3.1.3) lib/active_support/callbacks.rb:392:in `_run_call_callbacks'
activesupport (3.1.3) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.1.3) lib/action_dispatch/middleware/callbacks.rb:28:in `call'
actionpack (3.1.3) lib/action_dispatch/middleware/reloader.rb:68:in `call'
rack (1.3.6) lib/rack/sendfile.rb:101:in `call'
actionpack (3.1.3) lib/action_dispatch/middleware/remote_ip.rb:48:in `call'
actionpack (3.1.3) lib/action_dispatch/middleware/show_exceptions.rb:47:in `call'
railties (3.1.3) lib/rails/rack/logger.rb:13:in `call'
rack (1.3.6) lib/rack/methodoverride.rb:24:in `call'
rack (1.3.6) lib/rack/runtime.rb:17:in `call'
activesupport (3.1.3) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
rack (1.3.6) lib/rack/lock.rb:15:in `call'
actionpack (3.1.3) lib/action_dispatch/middleware/static.rb:53:in `call'
railties (3.1.3) lib/rails/engine.rb:456:in `call'
rack (1.3.6) lib/rack/content_length.rb:14:in `call'
rack (1.3.6) lib/rack/handler/webrick.rb:59:in `service'
/Users/jandrews/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/webrick/httpserver.rb:138:in `service'
/Users/jandrews/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/webrick/httpserver.rb:94:in `run'
/Users/jandrews/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/webrick/server.rb:191:in `block in start_thread'
Request
Parameters:
{"authenticity_token"=>"tx+PRUMMQpyZ48Yw9ZLoWZ60HOo1992tpQXbKFkF4YM=",
"product_id"=>"5"}
Show session dump
Show env dump
Response
Headers:
None
实际执行提交的代码在浏览器中显示如下
<form action="/line_items?product_id=5" class="button_to" method="post">
<div>
<input type="submit" value="Add to Cart">
<input name="authenticity_token" type="hidden"
value="tx+PRUMMQpyZ48Yw9ZLoWZ60HOo1992tpQXbKFkF4YM=">
</div>
</form>
很抱歉忘了提一下我是否从原来一行一个一行地添加了这行。因为我对红宝石的了解仍然有限，所以我能够调试。
@cart = current_cart
购物车模型文件。
class Cart < ActiveRecord::Base
has_many :line_items, dependent: destroy
end
答案 0 :(得分：5)
而不是
has_many :line_items, dependent: destroy
把
has_many :line_items, dependent: :destroy # the colon!!