索引动作演示者的初始化方法
initialize method for an index action presenter
我想为 Event 的索引操作创建演示者。
这是它的样子。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 %>
应用程序助手：
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
现在的情况是，演示者的初始化方法出现 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个没有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，应用程序在 application_helper 和 uninitialized constant ArrayPresenter 的 klass ||= 行中断，而它应该正在寻找 EventPresenter 常量。
完整跟踪：
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'
你似乎通过在视图层中调用 present 方法来用演示者包装 event 对象，所以在控制器中做同样的事情对我来说看起来是多余的。此外，这实际上是导致 wrong number of arguments 的一行，因为您仅用一个参数将其包装起来。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 class，您就会得到 "#{object.class}Presenter".constantize 结束使用 "ArrayPresenter".constantize，这会导致错误，因为没有像 ArrayPresenter 这样的 class。你在这里可以做的是先迭代一个数组来解决这个问题：
<% @events.each do |event| %>
<% present event do |event_presenter| %>
另一种选择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。
我想为 Event 的索引操作创建演示者。
这是它的样子。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 %>
应用程序助手：
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
现在的情况是，演示者的初始化方法出现 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个没有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，应用程序在 application_helper 和 uninitialized constant ArrayPresenter 的 klass ||= 行中断，而它应该正在寻找 EventPresenter 常量。
完整跟踪：
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'
你似乎通过在视图层中调用 present 方法来用演示者包装 event 对象，所以在控制器中做同样的事情对我来说看起来是多余的。此外，这实际上是导致 wrong number of arguments 的一行，因为您仅用一个参数将其包装起来。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 class，您就会得到 "#{object.class}Presenter".constantize 结束使用 "ArrayPresenter".constantize，这会导致错误，因为没有像 ArrayPresenter 这样的 class。你在这里可以做的是先迭代一个数组来解决这个问题：
<% @events.each do |event| %>
<% present event do |event_presenter| %>
另一种选择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。