索引操作演示者的初始化方法

【问题标题】：initialize method for an index action presenter索引操作演示者的初始化方法
【发布时间】：2016-10-19 14:45:17
【问题描述】：

我想为Event 的索引操作创建演示者。

这就是它的样子。将有更多的方法和东西添加到演示者和视图中，但现在我只想让它工作：

class EventPresenter

  def initialize(events, template)
    @events = events
    @template = template
  end

  def h
    @template
  end

  def event_title
    h.link_to event.name, event_path(event)
  end
end

index.html.erb：

<% present @events do |event_presenter| %> <tr>
    <td><%= event_presenter.event_title %></td>
<% end %>

应用助手：

module ApplicationHelper
  def present(object, klass = nil)
    klass ||= "#{object.class}Presenter".constantize
    presenter = klass.new(object, self)
    yield presenter if block_given?
    presenter
  end
end

events_controller：

  def index
    @events = Event.all.map{ |event| EventPresenter.new(event) }
   # render json: @events
  end

现在的情况，我收到了演示者初始化方法的wrong number of arguments (1 for 2) 错误。我试图通过删除@events 或@template 来查看两个对象中的哪一个没有被传递到初始化程序中，例如：

  def initialize(template)
    @template = template
  end

但是，在这两种情况下，应用程序都会在 application_helper 的 klass ||= 行以 uninitialized constant ArrayPresenter 中断，而它应该正在寻找 EventPresenter 常量。

完整的跟踪：

activesupport (5.0.0.beta3) lib/active_support/inflector/methods.rb:259:in `const_get'
activesupport (5.0.0.beta3) lib/active_support/inflector/methods.rb:259:in `block in constantize'
activesupport (5.0.0.beta3) lib/active_support/inflector/methods.rb:257:in `each'
activesupport (5.0.0.beta3) lib/active_support/inflector/methods.rb:257:in `inject'
activesupport (5.0.0.beta3) lib/active_support/inflector/methods.rb:257:in `constantize'
activesupport (5.0.0.beta3) lib/active_support/core_ext/string/inflections.rb:66:in `constantize'
app/helpers/application_helper.rb:3:in `present'
app/views/events/index.html.erb:1:in `_app_views_events_index_html_erb__1682590753278671208_70298040094320'
actionview (5.0.0.beta3) lib/action_view/template.rb:158:in `block in render'
activesupport (5.0.0.beta3) lib/active_support/notifications.rb:166:in `instrument'
actionview (5.0.0.beta3) lib/action_view/template.rb:348:in `instrument'
actionview (5.0.0.beta3) lib/action_view/template.rb:156:in `render'
actionview (5.0.0.beta3) lib/action_view/renderer/template_renderer.rb:54:in `block (2 levels) in render_template'
actionview (5.0.0.beta3) lib/action_view/renderer/abstract_renderer.rb:42:in `block in instrument'
activesupport (5.0.0.beta3) lib/active_support/notifications.rb:164:in `block in instrument'
activesupport (5.0.0.beta3) lib/active_support/notifications/instrumenter.rb:21:in `instrument'
activesupport (5.0.0.beta3) lib/active_support/notifications.rb:164:in `instrument'
actionview (5.0.0.beta3) lib/action_view/renderer/abstract_renderer.rb:41:in `instrument'
actionview (5.0.0.beta3) lib/action_view/renderer/template_renderer.rb:53:in `block in render_template'
actionview (5.0.0.beta3) lib/action_view/renderer/template_renderer.rb:61:in `render_with_layout'
actionview (5.0.0.beta3) lib/action_view/renderer/template_renderer.rb:52:in `render_template'
actionview (5.0.0.beta3) lib/action_view/renderer/template_renderer.rb:14:in `render'
actionview (5.0.0.beta3) lib/action_view/renderer/renderer.rb:42:in `render_template'
actionview (5.0.0.beta3) lib/action_view/renderer/renderer.rb:23:in `render'
actionview (5.0.0.beta3) lib/action_view/rendering.rb:103:in `_render_template'
actionpack (5.0.0.beta3) lib/action_controller/metal/streaming.rb:217:in `_render_template'
actionview (5.0.0.beta3) lib/action_view/rendering.rb:83:in `render_to_body'
actionpack (5.0.0.beta3) lib/action_controller/metal/rendering.rb:52:in `render_to_body'
actionpack (5.0.0.beta3) lib/action_controller/metal/renderers.rb:144:in `render_to_body'
actionpack (5.0.0.beta3) lib/abstract_controller/rendering.rb:25:in `render'
actionpack (5.0.0.beta3) lib/action_controller/metal/rendering.rb:36:in `render'
actionpack (5.0.0.beta3) lib/action_controller/metal/instrumentation.rb:43:in `block (2 levels) in render'
activesupport (5.0.0.beta3) lib/active_support/core_ext/benchmark.rb:12:in `block in ms'
/usr/local/Cellar/ruby/2.2.3/lib/ruby/2.2.0/benchmark.rb:303:in `realtime'
activesupport (5.0.0.beta3) lib/active_support/core_ext/benchmark.rb:12:in `ms'
actionpack (5.0.0.beta3) lib/action_controller/metal/instrumentation.rb:43:in `block in render'
actionpack (5.0.0.beta3) lib/action_controller/metal/instrumentation.rb:86:in `cleanup_view_runtime'
activerecord (5.0.0.beta3) lib/active_record/railties/controller_runtime.rb:25:in `cleanup_view_runtime'
actionpack (5.0.0.beta3) lib/action_controller/metal/instrumentation.rb:42:in `render'
actionpack (5.0.0.beta3) lib/action_controller/metal/implicit_render.rb:19:in `default_render'
actionpack (5.0.0.beta3) lib/action_controller/metal/basic_implicit_render.rb:4:in `block in send_action'
actionpack (5.0.0.beta3) lib/action_controller/metal/basic_implicit_render.rb:4:in `tap'
actionpack (5.0.0.beta3) lib/action_controller/metal/basic_implicit_render.rb:4:in `send_action'
actionpack (5.0.0.beta3) lib/abstract_controller/base.rb:183:in `process_action'
actionpack (5.0.0.beta3) lib/action_controller/metal/rendering.rb:30:in `process_action'
actionpack (5.0.0.beta3) lib/abstract_controller/callbacks.rb:20:in `block in process_action'
activesupport (5.0.0.beta3) lib/active_support/callbacks.rb:126:in `call'
activesupport (5.0.0.beta3) lib/active_support/callbacks.rb:126:in `call'
activesupport (5.0.0.beta3) lib/active_support/callbacks.rb:506:in `block (2 levels) in compile'
activesupport (5.0.0.beta3) lib/active_support/callbacks.rb:455:in `call'
activesupport (5.0.0.beta3) lib/active_support/callbacks.rb:455:in `call'
activesupport (5.0.0.beta3) lib/active_support/callbacks.rb:101:in `__run_callbacks__'
activesupport (5.0.0.beta3) lib/active_support/callbacks.rb:750:in `_run_process_action_callbacks'
activesupport (5.0.0.beta3) lib/active_support/callbacks.rb:90:in `run_callbacks'
actionpack (5.0.0.beta3) lib/abstract_controller/callbacks.rb:19:in `process_action'
actionpack (5.0.0.beta3) lib/action_controller/metal/rescue.rb:27:in `process_action'
actionpack (5.0.0.beta3) lib/action_controller/metal/instrumentation.rb:31:in `block in process_action'
activesupport (5.0.0.beta3) lib/active_support/notifications.rb:164:in `block in instrument'
activesupport (5.0.0.beta3) lib/active_support/notifications/instrumenter.rb:21:in `instrument'
activesupport (5.0.0.beta3) lib/active_support/notifications.rb:164:in `instrument'
actionpack (5.0.0.beta3) lib/action_controller/metal/instrumentation.rb:29:in `process_action'
actionpack (5.0.0.beta3) lib/action_controller/metal/params_wrapper.rb:248:in `process_action'
activerecord (5.0.0.beta3) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
actionpack (5.0.0.beta3) lib/abstract_controller/base.rb:128:in `process'
actionview (5.0.0.beta3) lib/action_view/rendering.rb:30:in `process'
actionpack (5.0.0.beta3) lib/action_controller/metal.rb:190:in `dispatch'
actionpack (5.0.0.beta3) lib/action_controller/metal.rb:262:in `dispatch'
actionpack (5.0.0.beta3) lib/action_dispatch/routing/route_set.rb:50:in `dispatch'
actionpack (5.0.0.beta3) lib/action_dispatch/routing/route_set.rb:32:in `serve'
actionpack (5.0.0.beta3) lib/action_dispatch/journey/router.rb:39:in `block in serve'
actionpack (5.0.0.beta3) lib/action_dispatch/journey/router.rb:26:in `each'
actionpack (5.0.0.beta3) lib/action_dispatch/journey/router.rb:26:in `serve'
actionpack (5.0.0.beta3) lib/action_dispatch/routing/route_set.rb:724:in `call'
actionview (5.0.0.beta3) lib/action_view/digestor.rb:12:in `call'
rack (2.0.0.alpha) lib/rack/etag.rb:25:in `call'
rack (2.0.0.alpha) lib/rack/conditional_get.rb:25:in `call'
rack (2.0.0.alpha) lib/rack/head.rb:12:in `call'
rack (2.0.0.alpha) lib/rack/session/abstract/id.rb:220:in `context'
rack (2.0.0.alpha) lib/rack/session/abstract/id.rb:214:in `call'
actionpack (5.0.0.beta3) lib/action_dispatch/middleware/cookies.rb:613:in `call'
activerecord (5.0.0.beta3) lib/active_record/query_cache.rb:36:in `call'
activerecord (5.0.0.beta3) lib/active_record/connection_adapters/abstract/connection_pool.rb:963:in `call'
activerecord (5.0.0.beta3) lib/active_record/migration.rb:558:in `call'
actionpack (5.0.0.beta3) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
activesupport (5.0.0.beta3) lib/active_support/callbacks.rb:97:in `__run_callbacks__'
activesupport (5.0.0.beta3) lib/active_support/callbacks.rb:750:in `_run_call_callbacks'
activesupport (5.0.0.beta3) lib/active_support/callbacks.rb:90:in `run_callbacks'
actionpack (5.0.0.beta3) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (5.0.0.beta3) lib/action_dispatch/middleware/reloader.rb:71:in `call'
actionpack (5.0.0.beta3) lib/action_dispatch/middleware/remote_ip.rb:79:in `call'
actionpack (5.0.0.beta3) lib/action_dispatch/middleware/debug_exceptions.rb:49:in `call'
web-console (3.1.1) lib/web_console/middleware.rb:131:in `call_app'
web-console (3.1.1) lib/web_console/middleware.rb:28:in `block in call'
web-console (3.1.1) lib/web_console/middleware.rb:18:in `catch'
web-console (3.1.1) lib/web_console/middleware.rb:18:in `call'
actionpack (5.0.0.beta3) lib/action_dispatch/middleware/show_exceptions.rb:31:in `call'
railties (5.0.0.beta3) lib/rails/rack/logger.rb:36:in `call_app'
railties (5.0.0.beta3) lib/rails/rack/logger.rb:24:in `block in call'
activesupport (5.0.0.beta3) lib/active_support/tagged_logging.rb:70:in `block in tagged'
activesupport (5.0.0.beta3) lib/active_support/tagged_logging.rb:26:in `tagged'
activesupport (5.0.0.beta3) lib/active_support/tagged_logging.rb:70:in `tagged'
railties (5.0.0.beta3) lib/rails/rack/logger.rb:24:in `call'
actionpack (5.0.0.beta3) lib/action_dispatch/middleware/request_id.rb:24:in `call'
rack (2.0.0.alpha) lib/rack/method_override.rb:22:in `call'
rack (2.0.0.alpha) lib/rack/runtime.rb:22:in `call'
activesupport (5.0.0.beta3) lib/active_support/cache/strategy/local_cache_middleware.rb:28:in `call'
actionpack (5.0.0.beta3) lib/action_dispatch/middleware/load_interlock.rb:13:in `call'
actionpack (5.0.0.beta3) lib/action_dispatch/middleware/static.rb:136:in `call'
rack (2.0.0.alpha) lib/rack/sendfile.rb:111:in `call'
railties (5.0.0.beta3) lib/rails/engine.rb:522:in `call'
puma (3.4.0) lib/puma/configuration.rb:224:in `call'
puma (3.4.0) lib/puma/server.rb:569:in `handle_request'
puma (3.4.0) lib/puma/server.rb:406:in `process_client'
puma (3.4.0) lib/puma/server.rb:271:in `block in run'
puma (3.4.0) lib/puma/thread_pool.rb:114:in `call'
puma (3.4.0) lib/puma/thread_pool.rb:114:in `block in spawn_thread'

【问题讨论】：

  • 你能发布堆栈跟踪吗？
  • 当然，我刚刚更新了帖子

标签： ruby-on-rails initialization presenter


【解决方案1】：

您似乎通过在视图层中调用 present 方法将 event 对象与演示者包装在一起，因此在控制器中执行相同的操作对我来说似乎是多余的。此外，这实际上是一条导致wrong number of arguments 的行，因为您只用一个参数包装了它。让我们删除它：

# events_controller
def index
  @events = Event.all
  # we removed redundant EventPresenter.new(event) here
end

下一步是您的视图模板。只要@events 包含一个元素数组（您可以在present 辅助方法中检查object 参数的类），您就会得到"#{object.class}Presenter".constantize 以"ArrayPresenter".constantize 结尾，这会导致错误为没有像ArrayPresenter 这样的类。你可以在这里解决这个问题是先迭代一个数组：

<% @events.each do |event| %>
  <% present event do |event_presenter| %>

另一种选择可能是在您的辅助方法中迭代一个集合。您可能会对Draper gem 等现有解决方案感兴趣，以了解它们如何解决对象包装问题。

【讨论】：

  • 好的，终于有时间尝试一下了。这一切都是有道理的，除了我应该在 EventPresenter 文件中更改什么？该应用程序在h.link_to event.name, event_path(event) 与undefined local variable or method event' 行发生故障，用于#
  • @sivanes 在该方法中没有像event 这样的局部变量，因此该错误似乎是合法的。你只有@events 数组。更重要的是，你会遇到从演示者类调用h 的问题（因为那里没有定义那个助手）。并且您在初始化程序中的template 参数是一个保留的rails 字，因此您可能应该重命名它。请注意，Presenter 是高级主题，您应该为大量此类问题做好准备。
  • 所以，这里没有快速修复，我接受？
  • uninitialized constant ArrayPresenter 错误应该由上述解决方案修复。其他问题超出了这个线程框架。
猜你喜欢
  • 2016-10-15
  • 1970-01-01
  • 2012-10-13
  • 1970-01-01
  • 1970-01-01
  • 2022-08-18
  • 1970-01-01
  • 1970-01-01
  • 2016-08-23
相关资源
最近更新 更多
热门标签
Java Python linux javascript Mysql C# Docker 算法 前端 SpringBoot Redis Vue spring 设计模式 .net core .net kubernetes c++ 数据库 数据结构 大数据 js 机器学习 微服务 Android Go 程序员 面试 JVM ASP.net core 云原生 人工智能 后端 PHP git CSS golang k8s Nginx Django mybatis 深度学习 多线程 React 架构 devops 爬虫 云计算 Spring Boot LeetCode