Question

我使用Ruby on Rails 4.1创建了一个票务预订应用程序作为我的示例项目。三个是三个模型 - 活动，门票和预订。活动有很多门票和预订。门票有很多预订，属于活动。预订属于活动和门票。

票证控制器如下所示：

class TicketsController < ApplicationController
def index
    @event = Event.find(params[:event_id])
    @tickets = @event.tickets.all
end

def show
    @event = Event.find(params[:event_id])
    @ticket = @event.tickets.find(params[:id])
end

def new
    @event = Event.find(params[:event_id])
    @ticket = Ticket.new
end

def create
    @event = Event.find(params[:event_id])
    @ticket = @event.tickets.create(ticket_params)
    if @ticket.save
        redirect_to [@event, @ticket]
    else
        render 'new'
    end
end

def edit
    @event = Event.find(params[:event_id])
    @ticket= @event.tickets.find(params[:id])
end

def update
    @event = Event.find(params[:event_id])
    @ticket = @event.tickets.find(params[:id])

    if @ticket.update(ticket_params)
        redirect_to [@event, @ticket]
    else
        render 'edit'
    end
end

def destroy
    @event = Event.find(params[:event_id])
    @ticket = @event.tickets.find(params[:id])
    @ticket.destroy
    redirect_to event_tickets_path
end


private

def ticket_params
    params.require(:ticket).permit(:ticket_name, :booking_start_date, :booking_end_date, :ticket_price, :ticket_quantity, :minimum_quantity, :maximum_quantity, :terms_conditions, :more_information)
end

端

票证模型如下所示

class Ticket < ActiveRecord::Base
 belongs_to :event
 has_many :bookings

 def maximum_tickets_allowed
    max = ticket.maximum_quantity.to_i
    self.maximum_quantity = (1..max).to_a
 end

   end

Tickets show文件如下所示：

<h2>Tickets</h2>

<p><%= @ticket.ticket_name %></p>
<p><%= @ticket.booking_start_date %></p>
<p><%= @ticket.booking_end_date %></p>
<p><%= @ticket.maximum_tickets_allowed %></p>

maxium_quantity是一个人可以预订的最大票数，我在此尝试将其转换为要在collection_select中使用的数组。

现在，如果我使用<%= @ticket.maximum_tickets_allowed %>，我会获得undefined method maximum_tickets_allowed＆＃39; error. I tried using self.maximum_tickets_allowed`，但它不起作用。我哪里错了？

错误的完整堆栈跟踪：

activemodel (4.1.1) lib/active_model/attribute_methods.rb:435:in `method_missing'
activerecord (4.1.1) lib/active_record/attribute_methods.rb:206:in `method_missing'
app/views/tickets/show.html.erb:6:in `_app_views_tickets_show_html_erb__2112154808966627486_70166705061960'
actionview (4.1.1) lib/action_view/template.rb:145:in `block in render'
activesupport (4.1.1) lib/active_support/notifications.rb:161:in `instrument'
actionview (4.1.1) lib/action_view/template.rb:339:in `instrument'
actionview (4.1.1) lib/action_view/template.rb:143:in `render'
actionview (4.1.1) lib/action_view/renderer/template_renderer.rb:55:in `block (2 levels) in render_template'
actionview (4.1.1) lib/action_view/renderer/abstract_renderer.rb:38:in `block in instrument'
activesupport (4.1.1) lib/active_support/notifications.rb:159:in `block in instrument'
activesupport (4.1.1) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
activesupport (4.1.1) lib/active_support/notifications.rb:159:in `instrument'
actionview (4.1.1) lib/action_view/renderer/abstract_renderer.rb:38:in `instrument'
actionview (4.1.1) lib/action_view/renderer/template_renderer.rb:54:in `block in render_template'
actionview (4.1.1) lib/action_view/renderer/template_renderer.rb:62:in `render_with_layout'
actionview (4.1.1) lib/action_view/renderer/template_renderer.rb:53:in `render_template'
actionview (4.1.1) lib/action_view/renderer/template_renderer.rb:17:in `render'
actionview (4.1.1) lib/action_view/renderer/renderer.rb:42:in `render_template'
actionview (4.1.1) lib/action_view/renderer/renderer.rb:23:in `render'
actionview (4.1.1) lib/action_view/rendering.rb:99:in `_render_template'
actionpack (4.1.1) lib/action_controller/metal/streaming.rb:217:in `_render_template'
actionview (4.1.1) lib/action_view/rendering.rb:82:in `render_to_body'
actionpack (4.1.1) lib/action_controller/metal/rendering.rb:32:in `render_to_body'
actionpack (4.1.1) lib/action_controller/metal/renderers.rb:32:in `render_to_body'
actionpack (4.1.1) lib/abstract_controller/rendering.rb:25:in `render'
actionpack (4.1.1) lib/action_controller/metal/rendering.rb:16:in `render'
actionpack (4.1.1) lib/action_controller/metal/instrumentation.rb:41:in `block (2 levels) in render'
activesupport (4.1.1) lib/active_support/core_ext/benchmark.rb:12:in `block in ms'
/Users/mohan/.rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/benchmark.rb:294:in `realtime'
activesupport (4.1.1) lib/active_support/core_ext/benchmark.rb:12:in `ms'
actionpack (4.1.1) lib/action_controller/metal/instrumentation.rb:41:in `block in render'
actionpack (4.1.1) lib/action_controller/metal/instrumentation.rb:84:in `cleanup_view_runtime'
activerecord (4.1.1) lib/active_record/railties/controller_runtime.rb:25:in `cleanup_view_runtime'
actionpack (4.1.1) lib/action_controller/metal/instrumentation.rb:40:in `render'
actionpack (4.1.1) lib/action_controller/metal/implicit_render.rb:10:in `default_render'
actionpack (4.1.1) lib/action_controller/metal/implicit_render.rb:5:in `send_action'
actionpack (4.1.1) lib/abstract_controller/base.rb:189:in `process_action'
actionpack (4.1.1) lib/action_controller/metal/rendering.rb:10:in `process_action'
actionpack (4.1.1) lib/abstract_controller/callbacks.rb:20:in `block in process_action'
activesupport (4.1.1) lib/active_support/callbacks.rb:113:in `call'
activesupport (4.1.1) lib/active_support/callbacks.rb:113:in `call'
activesupport (4.1.1) lib/active_support/callbacks.rb:229:in `block in halting'
activesupport (4.1.1) lib/active_support/callbacks.rb:229:in `call'
activesupport (4.1.1) lib/active_support/callbacks.rb:229:in `block in halting'
activesupport (4.1.1) lib/active_support/callbacks.rb:166:in `call'
activesupport (4.1.1) lib/active_support/callbacks.rb:166:in `block in halting'
activesupport (4.1.1) lib/active_support/callbacks.rb:166:in `call'
activesupport (4.1.1) lib/active_support/callbacks.rb:166:in `block in halting'
activesupport (4.1.1) lib/active_support/callbacks.rb:166:in `call'
activesupport (4.1.1) lib/active_support/callbacks.rb:166:in `block in halting'
activesupport (4.1.1) lib/active_support/callbacks.rb:86:in `call'
activesupport (4.1.1) lib/active_support/callbacks.rb:86:in `run_callbacks'
actionpack (4.1.1) lib/abstract_controller/callbacks.rb:19:in `process_action'
actionpack (4.1.1) lib/action_controller/metal/rescue.rb:29:in `process_action'
actionpack (4.1.1) lib/action_controller/metal/instrumentation.rb:31:in `block in process_action'
activesupport (4.1.1) lib/active_support/notifications.rb:159:in `block in instrument'
activesupport (4.1.1) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
activesupport (4.1.1) lib/active_support/notifications.rb:159:in `instrument'
actionpack (4.1.1) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
actionpack (4.1.1) lib/action_controller/metal/params_wrapper.rb:250:in `process_action'
activerecord (4.1.1) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
actionpack (4.1.1) lib/abstract_controller/base.rb:136:in `process'
actionview (4.1.1) lib/action_view/rendering.rb:30:in `process'
actionpack (4.1.1) lib/action_controller/metal.rb:195:in `dispatch'
actionpack (4.1.1) lib/action_controller/metal/rack_delegation.rb:13:in `dispatch'
actionpack (4.1.1) lib/action_controller/metal.rb:231:in `block in action'
actionpack (4.1.1) lib/action_dispatch/routing/route_set.rb:80:in `call'
actionpack (4.1.1) lib/action_dispatch/routing/route_set.rb:80:in `dispatch'
actionpack (4.1.1) lib/action_dispatch/routing/route_set.rb:48:in `call'
actionpack (4.1.1) lib/action_dispatch/journey/router.rb:71:in `block in call'
actionpack (4.1.1) lib/action_dispatch/journey/router.rb:59:in `each'
actionpack (4.1.1) lib/action_dispatch/journey/router.rb:59:in `call'
actionpack (4.1.1) lib/action_dispatch/routing/route_set.rb:676:in `call'
rack (1.5.2) lib/rack/etag.rb:23:in `call'
rack (1.5.2) lib/rack/conditionalget.rb:25:in `call'
rack (1.5.2) lib/rack/head.rb:11:in `call'
actionpack (4.1.1) lib/action_dispatch/middleware/params_parser.rb:27:in `call'
actionpack (4.1.1) lib/action_dispatch/middleware/flash.rb:254:in `call'
rack (1.5.2) lib/rack/session/abstract/id.rb:225:in `context'
rack (1.5.2) lib/rack/session/abstract/id.rb:220:in `call'
actionpack (4.1.1) lib/action_dispatch/middleware/cookies.rb:560:in `call'
activerecord (4.1.1) lib/active_record/query_cache.rb:36:in `call'
activerecord (4.1.1) lib/active_record/connection_adapters/abstract/connection_pool.rb:621:in `call'
activerecord (4.1.1) lib/active_record/migration.rb:380:in `call'
actionpack (4.1.1) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
activesupport (4.1.1) lib/active_support/callbacks.rb:82:in `run_callbacks'
actionpack (4.1.1) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (4.1.1) lib/action_dispatch/middleware/reloader.rb:73:in `call'
actionpack (4.1.1) lib/action_dispatch/middleware/remote_ip.rb:76:in `call'
actionpack (4.1.1) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
actionpack (4.1.1) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
railties (4.1.1) lib/rails/rack/logger.rb:38:in `call_app'
railties (4.1.1) lib/rails/rack/logger.rb:20:in `block in call'
activesupport (4.1.1) lib/active_support/tagged_logging.rb:68:in `block in tagged'
activesupport (4.1.1) lib/active_support/tagged_logging.rb:26:in `tagged'
activesupport (4.1.1) lib/active_support/tagged_logging.rb:68:in `tagged'
railties (4.1.1) lib/rails/rack/logger.rb:20:in `call'
actionpack (4.1.1) lib/action_dispatch/middleware/request_id.rb:21:in `call'
rack (1.5.2) lib/rack/methodoverride.rb:21:in `call'
rack (1.5.2) lib/rack/runtime.rb:17:in `call'
activesupport (4.1.1) lib/active_support/cache/strategy/local_cache_middleware.rb:26:in `call'
rack (1.5.2) lib/rack/lock.rb:17:in `call'
actionpack (4.1.1) lib/action_dispatch/middleware/static.rb:64:in `call'
rack (1.5.2) lib/rack/sendfile.rb:112:in `call'
railties (4.1.1) lib/rails/engine.rb:514:in `call'
railties (4.1.1) lib/rails/application.rb:144:in `call'
rack (1.5.2) lib/rack/lock.rb:17:in `call'
rack (1.5.2) lib/rack/content_length.rb:14:in `call'
rack (1.5.2) lib/rack/handler/webrick.rb:60:in `service'
/Users/mohan/.rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/webrick/httpserver.rb:138:in `service'
/Users/mohan/.rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/webrick/httpserver.rb:94:in `run'
/Users/mohan/.rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/webrick/server.rb:295:in `block in start_thread'

Answer 1

您在方法中调用ticket.maximum_quanitity，因为您使用的是故障单实例方法，它不仅仅是maximum_quantity吗？

Answer 2

要考虑的一些事情。

从评论中，听起来@ticket变量可能是零？我不确定@event.tickets.find(params[:id])是否会抛出ActiveRecord::RecordNotFoundError Ticket.find之类的event_id。你为控制器获取数据的方式有点像Rails方式。 Ticket和Event之间存在一对多的关系。无需将id和TicketsController#show传递给class TicketsController < ApplicationController def show @ticket = Ticket.find params[:id] @event = @ticket.event end end方法。只需传递票证ID：

Ticket.find

如果故障单不存在，使用ActiveRecord::RecordNotFoundError会引发Ticket.find。如果我没记错的话，Rails中的默认控制器错误处理应该捕获该特定异常并呈现404 Not Found页面，因此在@event之后，您可以确保拥有Ticket对象。

接下来，如果您仍需要@ticket.event实例变量，请使用ActiveRecord关系通过class Ticket < ActiveRecord::Base belongs_to :event has_many :bookings def maximum_tickets_allowed (1..self.maximum_quantity).to_a end end获取它。

现在模型本身需要以下代码：

maximum_tickets_allowed

def maximum_tickets_allowed Range.new(1, maximum_quantity).to_a end方法应该只返回一个数组。我还想知道方法调用作为Range的结束值是否正在绊倒Ruby解释器。您可以尝试直接实例化Range对象：

<h2>Tickets</h2>

<p><%= @ticket.ticket_name %></p>
<p><%= @ticket.booking_start_date %></p>
<p><%= @ticket.booking_end_date %></p>
<p><%= @ticket.maximum_tickets_allowed %></p>

视图保持不变：

show

编辑＃1：正如上面提到的评论一样，如果最近添加了数据库中的maximum_quantity列，请确保您已运行所有Active Record迁移，否则该方法将当Rails应用程序启动时，ActiveRecord不会自动生成。

编辑＃2：在您的find方法中，您正在查找事件，然后查找所有故障单并只获取该事件可用的其中一张故障单。由于您已获得该ID，然后从故障单对象中获取该事件，因此这不如获取故障单有效。

我没有找到有关ActiveRecord集合的{{1}}方法的任何文档，因此我无法验证其行为。

无法在视图中使用模型方法

2 个答案: