我正在尝试在更新模型失败时传递用户编辑的参数。 我的应用呈现操作使用format.html { render :edit_company}进行编辑，结果如下：
undefined 方法 'empty？' for nil：NilClass
错误指向我的选择，我现在不知道为什么。
在行动edit_company中，我设置了当前公司的州和城市，并通过了可用州和城市的列表来更新模型。
def edit_company
states = State.all
@state_company = @professional_company.professional_company_address.city.state.id
@city_company = @professional_company.professional_company_address.city.id
state = State.find(@state_company)
@list_cities = state.cities.map { |c| [c.name, c.id] }
@list_states = states.map { |s| [s.name, s.id] }.insert(0, 'Selecione o estado')
end
在我看来，我有两个帮手
<%= select(:state, @state_company, @list_states, {:selected => @state_company}, {class:"form-control m-input m-input--square", id:"stateSelect" })%>
<%= ff.select(:city_id, @list_cities , {selected:@city_company}, {class:"form-control m-input m-input--square", id:"city_id"}) %>
完整的错误堆栈为：
NoMethodError - undefined method `empty?' for nil:NilClass:
actionview (5.1.4) lib/action_view/helpers/tags/select.rb:36:in `grouped_choices?'
actionview (5.1.4) lib/action_view/helpers/tags/select.rb:20:in `render'
actionview (5.1.4) lib/action_view/helpers/form_options_helper.rb:163:in `select'
app/views/professional/companies/_form.html.erb:195:in `block in _app_views_professional_companies__form_html_erb__1642623332971831228_47080343822700'
actionview (5.1.4) lib/action_view/helpers/capture_helper.rb:39:in `block in capture'
actionview (5.1.4) lib/action_view/helpers/capture_helper.rb:203:in `with_output_buffer'
actionview (5.1.4) lib/action_view/helpers/capture_helper.rb:39:in `capture'
actionview (5.1.4) lib/action_view/helpers/form_helper.rb:758:in `form_with'
app/views/professional/companies/_form.html.erb:45:in `_app_views_professional_companies__form_html_erb__1642623332971831228_47080343822700'
actionview (5.1.4) lib/action_view/template.rb:157:in `block in render'
activesupport (5.1.4) lib/active_support/notifications.rb:168:in `instrument'
actionview (5.1.4) lib/action_view/template.rb:352:in `instrument_render_template'
actionview (5.1.4) lib/action_view/template.rb:155:in `render'
actionview (5.1.4) lib/action_view/renderer/partial_renderer.rb:342:in `block in render_partial'
actionview (5.1.4) lib/action_view/renderer/abstract_renderer.rb:42:in `block in instrument'
activesupport (5.1.4) lib/active_support/notifications.rb:166:in `block in instrument'
activesupport (5.1.4) lib/active_support/notifications/instrumenter.rb:21:in `instrument'
activesupport (5.1.4) lib/active_support/notifications.rb:166:in `instrument'
actionview (5.1.4) lib/action_view/renderer/abstract_renderer.rb:41:in `instrument'
actionview (5.1.4) lib/action_view/renderer/partial_renderer.rb:331:in `render_partial'
actionview (5.1.4) lib/action_view/renderer/partial_renderer.rb:310:in `render'
actionview (5.1.4) lib/action_view/renderer/renderer.rb:47:in `render_partial'
actionview (5.1.4) lib/action_view/helpers/rendering_helper.rb:35:in `render'
app/views/professional/companies/edit_company.html.erb:1:in `_app_views_professional_companies_edit_company_html_erb___4525412059839984133_69861543274900'
actionview (5.1.4) lib/action_view/template.rb:157:in `block in render'
activesupport (5.1.4) lib/active_support/notifications.rb:168:in `instrument'
actionview (5.1.4) lib/action_view/template.rb:352:in `instrument_render_template'
actionview (5.1.4) lib/action_view/template.rb:155:in `render'
actionview (5.1.4) lib/action_view/renderer/template_renderer.rb:52:in `block (2 levels) in render_template'
actionview (5.1.4) lib/action_view/renderer/abstract_renderer.rb:42:in `block in instrument'
activesupport (5.1.4) lib/active_support/notifications.rb:166:in `block in instrument'
activesupport (5.1.4) lib/active_support/notifications/instrumenter.rb:21:in `instrument'
activesupport (5.1.4) lib/active_support/notifications.rb:166:in `instrument'
actionview (5.1.4) lib/action_view/renderer/abstract_renderer.rb:41:in `instrument'
actionview (5.1.4) lib/action_view/renderer/template_renderer.rb:51:in `block in render_template'
actionview (5.1.4) lib/action_view/renderer/template_renderer.rb:59:in `render_with_layout'
actionview (5.1.4) lib/action_view/renderer/template_renderer.rb:50:in `render_template'
actionview (5.1.4) lib/action_view/renderer/template_renderer.rb:14:in `render'
actionview (5.1.4) lib/action_view/renderer/renderer.rb:42:in `render_template'
actionview (5.1.4) lib/action_view/renderer/renderer.rb:23:in `render'
actionview (5.1.4) lib/action_view/rendering.rb:103:in `_render_template'
actionpack (5.1.4) lib/action_controller/metal/streaming.rb:217:in `_render_template'
actionview (5.1.4) lib/action_view/rendering.rb:83:in `render_to_body'
actionpack (5.1.4) lib/action_controller/metal/rendering.rb:52:in `render_to_body'
actionpack (5.1.4) lib/action_controller/metal/renderers.rb:141:in `render_to_body'
actionpack (5.1.4) lib/abstract_controller/rendering.rb:24:in `render'
actionpack (5.1.4) lib/action_controller/metal/rendering.rb:36:in `render'
actionpack (5.1.4) lib/action_controller/metal/instrumentation.rb:44:in `block (2 levels) in render'
activesupport (5.1.4) lib/active_support/core_ext/benchmark.rb:12:in `block in ms'
/home/leonardo/.rbenv/versions/2.4.2/lib/ruby/2.4.0/benchmark.rb:308:in `realtime'
activesupport (5.1.4) lib/active_support/core_ext/benchmark.rb:12:in `ms'
actionpack (5.1.4) lib/action_controller/metal/instrumentation.rb:44:in `block in render'
actionpack (5.1.4) lib/action_controller/metal/instrumentation.rb:87:in `cleanup_view_runtime'
searchkick (2.3.2) lib/searchkick/logging.rb:214:in `cleanup_view_runtime'
activerecord (5.1.4) lib/active_record/railties/controller_runtime.rb:29:in `cleanup_view_runtime'
actionpack (5.1.4) lib/action_controller/metal/instrumentation.rb:43:in `render'
app/controllers/professional/companies_controller.rb:134:in `block (2 levels) in update'
actionpack (5.1.4) lib/action_controller/metal/mime_responds.rb:201:in `respond_to'
app/controllers/professional/companies_controller.rb:128:in `update'
actionpack (5.1.4) lib/action_controller/metal/basic_implicit_render.rb:4:in `send_action'
actionpack (5.1.4) lib/abstract_controller/base.rb:186:in `process_action'
actionpack (5.1.4) lib/action_controller/metal/rendering.rb:30:in `process_action'
actionpack (5.1.4) lib/abstract_controller/callbacks.rb:20:in `block in process_action'
activesupport (5.1.4) lib/active_support/callbacks.rb:131:in `run_callbacks'
actionpack (5.1.4) lib/abstract_controller/callbacks.rb:19:in `process_action'
actionpack (5.1.4) lib/action_controller/metal/rescue.rb:20:in `process_action'
actionpack (5.1.4) lib/action_controller/metal/instrumentation.rb:32:in `block in process_action'
activesupport (5.1.4) lib/active_support/notifications.rb:166:in `block in instrument'
activesupport (5.1.4) lib/active_support/notifications/instrumenter.rb:21:in `instrument'
activesupport (5.1.4) lib/active_support/notifications.rb:166:in `instrument'
actionpack (5.1.4) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
actionpack (5.1.4) lib/action_controller/metal/params_wrapper.rb:252:in `process_action'
searchkick (2.3.2) lib/searchkick/logging.rb:209:in `process_action'
activerecord (5.1.4) lib/active_record/railties/controller_runtime.rb:22:in `process_action'
actionpack (5.1.4) lib/abstract_controller/base.rb:124:in `process'
actionview (5.1.4) lib/action_view/rendering.rb:30:in `process'
actionpack (5.1.4) lib/action_controller/metal.rb:189:in `dispatch'
actionpack (5.1.4) lib/action_controller/metal.rb:253:in `dispatch'
actionpack (5.1.4) lib/action_dispatch/routing/route_set.rb:49:in `dispatch'
actionpack (5.1.4) lib/action_dispatch/routing/route_set.rb:31:in `serve'
actionpack (5.1.4) lib/action_dispatch/journey/router.rb:50:in `block in serve'
actionpack (5.1.4) lib/action_dispatch/journey/router.rb:33:in `serve'
actionpack (5.1.4) lib/action_dispatch/routing/route_set.rb:834:in `call'
warden (1.2.7) lib/warden/manager.rb:36:in `block in call'
warden (1.2.7) lib/warden/manager.rb:35:in `call'
rack (2.0.3) lib/rack/etag.rb:25:in `call'
rack (2.0.3) lib/rack/conditional_get.rb:38:in `call'
rack (2.0.3) lib/rack/head.rb:12:in `call'
rack (2.0.3) lib/rack/session/abstract/id.rb:232:in `context'
rack (2.0.3) lib/rack/session/abstract/id.rb:226:in `call'
actionpack (5.1.4) lib/action_dispatch/middleware/cookies.rb:613:in `call'
activerecord (5.1.4) lib/active_record/migration.rb:556:in `call'
actionpack (5.1.4) lib/action_dispatch/middleware/callbacks.rb:26:in `block in call'
activesupport (5.1.4) lib/active_support/callbacks.rb:97:in `run_callbacks'
actionpack (5.1.4) lib/action_dispatch/middleware/callbacks.rb:24:in `call'
actionpack (5.1.4) lib/action_dispatch/middleware/executor.rb:12:in `call'
better_errors (2.3.0) lib/better_errors/middleware.rb:84:in `protected_app_call'
better_errors (2.3.0) lib/better_errors/middleware.rb:79:in `better_errors_call'
better_errors (2.3.0) lib/better_errors/middleware.rb:57:in `call'
actionpack (5.1.4) lib/action_dispatch/middleware/debug_exceptions.rb:59:in `call'
web-console (3.5.1) lib/web_console/middleware.rb:135:in `call_app'
web-console (3.5.1) lib/web_console/middleware.rb:28:in `block in call'
web-console (3.5.1) lib/web_console/middleware.rb:18:in `call'
actionpack (5.1.4) lib/action_dispatch/middleware/show_exceptions.rb:31:in `call'
railties (5.1.4) lib/rails/rack/logger.rb:36:in `call_app'
railties (5.1.4) lib/rails/rack/logger.rb:24:in `block in call'
activesupport (5.1.4) lib/active_support/tagged_logging.rb:69:in `block in tagged'
activesupport (5.1.4) lib/active_support/tagged_logging.rb:26:in `tagged'
activesupport (5.1.4) lib/active_support/tagged_logging.rb:69:in `tagged'
railties (5.1.4) lib/rails/rack/logger.rb:24:in `call'
sprockets-rails (3.2.1) lib/sprockets/rails/quiet_assets.rb:13:in `call'
actionpack (5.1.4) lib/action_dispatch/middleware/remote_ip.rb:79:in `call'
actionpack (5.1.4) lib/action_dispatch/middleware/request_id.rb:25:in `call'
rack (2.0.3) lib/rack/method_override.rb:22:in `call'
rack (2.0.3) lib/rack/runtime.rb:22:in `call'
activesupport (5.1.4) lib/active_support/cache/strategy/local_cache_middleware.rb:27:in `call'
actionpack (5.1.4) lib/action_dispatch/middleware/executor.rb:12:in `call'
actionpack (5.1.4) lib/action_dispatch/middleware/static.rb:125:in `call'
rack (2.0.3) lib/rack/sendfile.rb:111:in `call'
railties (5.1.4) lib/rails/engine.rb:522:in `call'
puma (3.10.0) lib/puma/configuration.rb:225:in `call'
puma (3.10.0) lib/puma/server.rb:605:in `handle_request'
puma (3.10.0) lib/puma/server.rb:437:in `process_client'
puma (3.10.0) lib/puma/server.rb:301:in `block in run'
puma (3.10.0) lib/puma/thread_pool.rb:120:in `block in spawn_thread'
我认为您的主要问题在于您在更新失败状态下说您正在这样做：
format.html { render :edit_company}
但是，这只会呈现edit_companyHTML 模板 - 它也不会运行edit_company操作(其中所有选择的查找数组都已初始化)。这就是为什么它们在呈现模板时为零的原因。
相反，您应该将诸如选择查找之类的常见逻辑移动到另一个方法，假设您将其称为load_cities_and_states，然后您可以直接从edit_company和update调用它，或者更好的是，您可以在控制器顶部使用before_action引用：
class CompanyController < ApplicationController
before_action :load_cities_and_states, only: [:edit_company, :update]
end
以上将确保在edit_company和update之前运行load_cities_and_states。
注：注：我注意到您当前的代码引用了一个未在edit_company中定义的@professional_company变量，所以我想那一定也是在某处before_action中初始化的东西，或者可能是您的用户授权的一部分。确保在此之后发生load_cities_and_states，以便@professional_company存在，否则您将遇到另一个undefined method on NilClass错误。
希望对您有所帮助！
空？是Array上的Ruby方法，因此不能在nil对象上调用它。
在某个地方，您的代码需要一个数组并且正在接收 nil，因此试图调用空？ 在它引发错误。
也不要使用 map，这是一种 ruby 方法，就像你在控制器中所做的那样，因为它会脱离 SQL 并下降到 ruby。
相反，使用pluck，它将保持SQL格式的调用。
坏
@list_cities = state.cities.map { |c| [c.name, c.id] }
更好
@list_cities = state.cities.pluck(:name, :id)
此外，您在实例变量上插入@list_states也是 IMO 不好的。
如果需要插入另一个值，则应在帮助程序方法中执行此操作。最好通过返回一个新对象来改变当前对象。这将允许您在代码中的其他位置重用@list_states。
我认为这也是您的 nil 出现的地方，因为您在索引 0 处插入一个字符串而不是 id 和名称数组。
错
insert(0, 'Selecione o estado')
可能正确
insert(0, [0, 'Selecione o estado'])