Ruby-on-rails ArgumentError：ApplicationController 的副本已从模块树中删除但仍处于活动状态

ArgumentError: A copy of ApplicationController has been removed from the module tree but is still active

提问by Subhash Bhushan

I am using ActiveAdmin (with customized gemset for Rails 4) with Rails 4.0.0.rc2. Application also has custom-built authorization code based on railscasts #385and #386.

我在 Rails 4.0.0.rc2 中使用 ActiveAdmin（带有为 Rails 4 定制的 gemset）。应用程序还具有基于 railscasts #385和#386 的定制授权代码。

When I change something in a ActiveAdmin resource file and try to refresh the browser page, I get this error at the current_permissionmethod:

当我更改 ActiveAdmin 资源文件中的某些内容并尝试刷新浏览器页面时，我在该current_permission方法中收到此错误：

ArgumentError at /admin/courses

A copy of ApplicationController has been removed from the module tree but is still active!

/admin/courses 中的 ArgumentError

ApplicationController 的副本已从模块树中删除，但仍处于活动状态！

If I try a refresh again, I get:

如果我再次尝试刷新，我会得到：

Circular dependency detected while autoloading constant Permissions

自动加载常量权限时检测到循环依赖

I think this problem has something to do with autoloading of classes in development mode, after a change in the source file. I have seen similar problem posts, but they are for rails 2.3.x. Also, the solution seems to be specifying unloadablein the controller throwing this error, but I am not sure where to put in this snippet in ActiveAdmin.

我认为这个问题与在更改源文件后在开发模式下自动加载类有关。我看过类似的问题帖子，但它们是针对 rails 2.3.x 的。此外，该解决方案似乎unloadable在控制器中指定抛出此错误，但我不确定在 ActiveAdmin 中将此代码段放在何处。

This might not have anything to do with ActiveAdmin either. It might be about how Permissions class has been built and its usage within Application Controller. If I add a skip_before_filter :authorizein the ActiveAdmin resource class, this error vanishes.

这也可能与 ActiveAdmin 无关。它可能与权限类的构建方式及其在应用程序控制器中的使用有关。如果我skip_before_filter :authorize在 ActiveAdmin 资源类中添加一个，这个错误就会消失。

ApplicationController:

应用控制器：

class ApplicationController < ActionController::Base
  # Prevent CSRF attacks by raising an exception.
  # For APIs, you may want to use :null_session instead.
  protect_from_forgery with: :exception

  before_filter :authenticate_user!
  before_filter :authorize

  delegate :allow_action?, to: :current_permission
  helper_method :allow_action?

  delegate :allow_param?, to: :current_permission
  helper_method :allow_param?

  private
    def current_permission
      @current_permission ||= Permissions.permission_for(current_user)
    end

    def current_resource
      nil
    end

    def authorize
      if current_permission.allow_action?(params[:controller], params[:action], current_resource)
        current_permission.permit_params! params
      else
        redirect_to root_url, alert: "Not authorized."
      end
    end
end

Permissions.rb:

权限.rb：

module Permissions
  def self.permission_for(user)
    if user.nil?
      GuestPermission.new
    elsif user.admin?
      AdminPermission.new(user)
    else
      UserPermission.new(user)
    end
  end
end

admin/courses.rb:

管理员/courses.rb：

ActiveAdmin.register Course do
  index do
    column :name
    column :description
    column :duration
    column :status
    column :price
    default_actions
  end

  filter :discipline
  filter :level
  filter :lessons
  filter :name
  filter :status
end

Gemfile (relevant lines):

Gemfile（相关行）：

gem 'rails', '4.0.0.rc2'

# Use puma as the app server
gem 'puma'

# Administration - Temporary github refs until rails 4 compatible releases
gem 'responders',          github: 'plataformatec/responders'
gem 'inherited_resources', github: 'josevalim/inherited_resources'
gem 'ransack',             github: 'ernie/ransack',            branch: 'rails-4'
gem 'activeadmin',         github: 'gregbell/active_admin', branch: 'rails4'
gem 'formtastic',          github: 'justinfrench/formtastic'

ArgumentError:

参数错误：

ArgumentError - A copy of ApplicationController has been removed from the module tree but is still active!:
  activesupport (4.0.0.rc2) lib/active_support/dependencies.rb:445:in `load_missing_constant'
  activesupport (4.0.0.rc2) lib/active_support/dependencies.rb:183:in `const_missing'
  rspec-core (2.13.1) lib/rspec/core/backward_compatibility.rb:24:in `const_missing'
  app/controllers/application_controller.rb:17:in `current_permission'
  app/controllers/application_controller.rb:25:in `authorize'
  activesupport (4.0.0.rc2) lib/active_support/callbacks.rb:417:in `_run__1040990970961152968__process_action__callbacks'
  activesupport (4.0.0.rc2) lib/active_support/callbacks.rb:80:in `run_callbacks'
  actionpack (4.0.0.rc2) lib/abstract_controller/callbacks.rb:17:in `process_action'
  actionpack (4.0.0.rc2) lib/action_controller/metal/rescue.rb:29:in `process_action'
  actionpack (4.0.0.rc2) lib/action_controller/metal/instrumentation.rb:31:in `block in process_action'
  activesupport (4.0.0.rc2) lib/active_support/notifications.rb:159:in `block in instrument'
  activesupport (4.0.0.rc2) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
  activesupport (4.0.0.rc2) lib/active_support/notifications.rb:159:in `instrument'
  actionpack (4.0.0.rc2) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
  actionpack (4.0.0.rc2) lib/action_controller/metal/params_wrapper.rb:245:in `process_action'
  activerecord (4.0.0.rc2) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
  actionpack (4.0.0.rc2) lib/abstract_controller/base.rb:136:in `process'
  actionpack (4.0.0.rc2) lib/abstract_controller/rendering.rb:44:in `process'
  actionpack (4.0.0.rc2) lib/action_controller/metal.rb:195:in `dispatch'
  actionpack (4.0.0.rc2) lib/action_controller/metal/rack_delegation.rb:13:in `dispatch'
  actionpack (4.0.0.rc2) lib/action_controller/metal.rb:231:in `block in action'
  actionpack (4.0.0.rc2) lib/action_dispatch/routing/route_set.rb:80:in `dispatch'
  actionpack (4.0.0.rc2) lib/action_dispatch/routing/route_set.rb:48:in `call'
  actionpack (4.0.0.rc2) lib/action_dispatch/journey/router.rb:71:in `block in call'
  actionpack (4.0.0.rc2) lib/action_dispatch/journey/router.rb:59:in `call'
  actionpack (4.0.0.rc2) lib/action_dispatch/routing/route_set.rb:655:in `call'
  omniauth (1.1.4) lib/omniauth/strategy.rb:184:in `call!'
  omniauth (1.1.4) lib/omniauth/strategy.rb:164:in `call'
  omniauth (1.1.4) lib/omniauth/strategy.rb:184:in `call!'
  omniauth (1.1.4) lib/omniauth/strategy.rb:164:in `call'
  omniauth (1.1.4) lib/omniauth/strategy.rb:184:in `call!'
  omniauth (1.1.4) lib/omniauth/strategy.rb:164:in `call'
  newrelic_rpm (3.6.4.122) lib/new_relic/rack/error_collector.rb:12:in `call'
  newrelic_rpm (3.6.4.122) lib/new_relic/rack/agent_hooks.rb:22:in `call'
  newrelic_rpm (3.6.4.122) lib/new_relic/rack/browser_monitoring.rb:16:in `call'
  newrelic_rpm (3.6.4.122) lib/new_relic/rack/developer_mode.rb:28:in `call'
  meta_request (0.2.7) lib/meta_request/middlewares/app_request_handler.rb:13:in `call'
  rack-contrib (1.1.0) lib/rack/contrib/response_headers.rb:17:in `call'
  meta_request (0.2.7) lib/meta_request/middlewares/headers.rb:16:in `call'
  meta_request (0.2.7) lib/meta_request/middlewares/meta_request_handler.rb:13:in `call'
  warden (1.2.1) lib/warden/manager.rb:35:in `block in call'
  warden (1.2.1) lib/warden/manager.rb:34: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 (4.0.0.rc2) lib/action_dispatch/middleware/params_parser.rb:27:in `call'
  actionpack (4.0.0.rc2) lib/action_dispatch/middleware/flash.rb:241: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 (4.0.0.rc2) lib/action_dispatch/middleware/cookies.rb:486:in `call'
  activerecord (4.0.0.rc2) lib/active_record/query_cache.rb:36:in `call'
  activerecord (4.0.0.rc2) lib/active_record/connection_adapters/abstract/connection_pool.rb:626:in `call'
  activerecord (4.0.0.rc2) lib/active_record/migration.rb:369:in `call'
  actionpack (4.0.0.rc2) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
  activesupport (4.0.0.rc2) lib/active_support/callbacks.rb:373:in `_run__2183739952227501342__call__callbacks'
  activesupport (4.0.0.rc2) lib/active_support/callbacks.rb:80:in `run_callbacks'
  actionpack (4.0.0.rc2) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
  actionpack (4.0.0.rc2) lib/action_dispatch/middleware/reloader.rb:64:in `call'
  actionpack (4.0.0.rc2) lib/action_dispatch/middleware/remote_ip.rb:76:in `call'
  better_errors (0.9.0) lib/better_errors/middleware.rb:84:in `protected_app_call'
  better_errors (0.9.0) lib/better_errors/middleware.rb:79:in `better_errors_call'
  better_errors (0.9.0) lib/better_errors/middleware.rb:56:in `call'
  actionpack (4.0.0.rc2) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
  actionpack (4.0.0.rc2) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
  railties (4.0.0.rc2) lib/rails/rack/logger.rb:38:in `call_app'
  railties (4.0.0.rc2) lib/rails/rack/logger.rb:21:in `block in call'
  activesupport (4.0.0.rc2) lib/active_support/tagged_logging.rb:67:in `block in tagged'
  activesupport (4.0.0.rc2) lib/active_support/tagged_logging.rb:25:in `tagged'
  activesupport (4.0.0.rc2) lib/active_support/tagged_logging.rb:67:in `tagged'
  railties (4.0.0.rc2) lib/rails/rack/logger.rb:21:in `call'
  actionpack (4.0.0.rc2) 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 (4.0.0.rc2) lib/active_support/cache/strategy/local_cache.rb:83:in `call'
  rack (1.5.2) lib/rack/lock.rb:17:in `call'
  actionpack (4.0.0.rc2) lib/action_dispatch/middleware/static.rb:64:in `call'
  railties (4.0.0.rc2) lib/rails/engine.rb:511:in `call'
  railties (4.0.0.rc2) lib/rails/application.rb:97:in `call'
  rack (1.5.2) lib/rack/content_length.rb:14:in `call'
  puma (2.1.1) lib/puma/server.rb:369:in `handle_request'
  puma (2.1.1) lib/puma/server.rb:246:in `process_client'
  puma (2.1.1) lib/puma/server.rb:145:in `block in run'
  puma (2.1.1) lib/puma/thread_pool.rb:92:in `block in spawn_thread'

RuntimeError: Circular Dependency:

运行时错误：循环依赖：

RuntimeError - Circular dependency detected while autoloading constant Permissions:
  activesupport (4.0.0.rc2) lib/active_support/dependencies.rb:460:in `load_missing_constant'
  activesupport (4.0.0.rc2) lib/active_support/dependencies.rb:183:in `const_missing'
  rspec-core (2.13.1) lib/rspec/core/backward_compatibility.rb:24:in `const_missing'
  activesupport (4.0.0.rc2) lib/active_support/dependencies.rb:686:in `remove_constant'
  activesupport (4.0.0.rc2) lib/active_support/dependencies.rb:516:in `block in remove_unloadable_constants!'
  activesupport (4.0.0.rc2) lib/active_support/dependencies.rb:516:in `remove_unloadable_constants!'
  activesupport (4.0.0.rc2) lib/active_support/dependencies.rb:300:in `clear'
  railties (4.0.0.rc2) lib/rails/application/finisher.rb:90:in `block (2 levels) in <module:Finisher>'
  activesupport (4.0.0.rc2) lib/active_support/file_update_checker.rb:75:in `execute'
  railties (4.0.0.rc2) lib/rails/application/finisher.rb:105:in `block (2 levels) in <module:Finisher>'
  activesupport (4.0.0.rc2) lib/active_support/callbacks.rb:377:in `_run__2753119820186226816__prepare__callbacks'
  activesupport (4.0.0.rc2) lib/active_support/callbacks.rb:80:in `run_callbacks'
  actionpack (4.0.0.rc2) lib/action_dispatch/middleware/reloader.rb:74:in `prepare!'
  actionpack (4.0.0.rc2) lib/action_dispatch/middleware/reloader.rb:62:in `call'
  actionpack (4.0.0.rc2) lib/action_dispatch/middleware/remote_ip.rb:76:in `call'
  better_errors (0.9.0) lib/better_errors/middleware.rb:84:in `protected_app_call'
  better_errors (0.9.0) lib/better_errors/middleware.rb:79:in `better_errors_call'
  better_errors (0.9.0) lib/better_errors/middleware.rb:56:in `call'
  actionpack (4.0.0.rc2) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
  actionpack (4.0.0.rc2) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
  railties (4.0.0.rc2) lib/rails/rack/logger.rb:38:in `call_app'
  railties (4.0.0.rc2) lib/rails/rack/logger.rb:21:in `block in call'
  activesupport (4.0.0.rc2) lib/active_support/tagged_logging.rb:67:in `block in tagged'
  activesupport (4.0.0.rc2) lib/active_support/tagged_logging.rb:25:in `tagged'
  activesupport (4.0.0.rc2) lib/active_support/tagged_logging.rb:67:in `tagged'
  railties (4.0.0.rc2) lib/rails/rack/logger.rb:21:in `call'
  actionpack (4.0.0.rc2) 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 (4.0.0.rc2) lib/active_support/cache/strategy/local_cache.rb:83:in `call'
  rack (1.5.2) lib/rack/lock.rb:17:in `call'
  actionpack (4.0.0.rc2) lib/action_dispatch/middleware/static.rb:64:in `call'
  railties (4.0.0.rc2) lib/rails/engine.rb:511:in `call'
  railties (4.0.0.rc2) lib/rails/application.rb:97:in `call'
  rack (1.5.2) lib/rack/content_length.rb:14:in `call'
  puma (2.1.1) lib/puma/server.rb:369:in `handle_request'
  puma (2.1.1) lib/puma/server.rb:246:in `process_client'
  puma (2.1.1) lib/puma/server.rb:145:in `block in run'
  puma (2.1.1) lib/puma/thread_pool.rb:92:in `block in spawn_thread'

Any clue will help. Let me know if you need to view other code snippets in the application.

任何线索都会有所帮助。如果您需要查看应用程序中的其他代码片段，请告诉我。

回答by Robert Falkén

For future visitors, I thought I'd provide some clarification on the original problem even though the question is pretty old and there is already an accepted answer.

对于未来的访问者，我想我会对原始问题提供一些说明，即使这个问题已经很老了并且已经有一个公认的答案。

The ArgumentError: A copy of X has been removed from the module tree but is still activeis raised when you are trying to access an automatically reloaded class (in app directory) from one that is not automatically reloaded (in lib directory).

在ArgumentError: A copy of X has been removed from the module tree but is still active当你从一个不会自动重新加载（在lib目录）试图访问一个自动加载类（在应用程序目录）提高。

回答by seanlinsley

I'm not sure exactly why this is happening, but I found a workaound. Change this:

我不确定为什么会发生这种情况，但我找到了一个解决方法。改变这个：

def current_permission
  @current_permission ||= Permissions.permission_for(current_user)
end

To this:

对此：

def current_permission
  @current_permission ||= ::Permissions.permission_for(current_user)
end

The error is raised at this point in ActiveSupport:

此时在 ActiveSupport 中引发错误：

# Load the constant named +const_name+ which is missing from +from_mod+. If
# it is not possible to load the constant into from_mod, try its parent
# module using +const_missing+.
def load_missing_constant(from_mod, const_name)
  log_call from_mod, const_name

  unless qualified_const_defined?(from_mod.name) && Inflector.constantize(from_mod.name).equal?(from_mod)
    raise ArgumentError, "A copy of #{from_mod} has been removed from the module tree but is still active!"
  end
  # ...
end

The problem only occurs when you don't fully qualify the constant name, so Rails tries looking it up in the ApplicationControllernamespace.

只有当您没有完全限定常量名称时才会出现问题，因此 Rails 尝试在ApplicationController命名空间中查找它。

回答by AP Fritts

I am not using ActiveAdmin, but I just experienced a circular dependency with ApplicationController.

我没有使用 ActiveAdmin，但我刚刚经历了对 ApplicationController 的循环依赖。

The problem was a helper module was declared improperly:

问题是辅助模块声明不正确：

app/helpers/home_helper.rb

was declared with:

声明为：

module StaticHelper

After fixing this, everything was peachy. I did not research why this happened and Rails didn't return a more intelligent error message.

解决这个问题后，一切都很美好。我没有研究为什么会发生这种情况，Rails 也没有返回更智能的错误消息。

回答by vatsal

In you development.rb temporarily try putting

在你 development.rb 暂时试试放

config.cache_classes = true

It worked for me.

它对我有用。

回答by monteirobrena

You can try put this line in your config/initializers/active_admin.rb:

您可以尝试将此行放在您的config/initializers/active_admin.rb：

In Rails <= 4:

在 Rails <= 4 中：

 config.skip_before_filter :load_footer_variables

In Rails >= 5

在 Rails 中 >= 5

config.skip_before_action :load_footer_variables

Like suggested here.

就像这里建议的那样。