未初始化的常量 ActiveSupport::EventedFileUpdateChecker (NameError) - [learn-ruby-on-rails] 教程

Question

我正在关注 Daniel Kehoe 的“Learn Ruby on Rails”一书。我似乎无法超越第 10 章的结尾，第 11 章的开始，我在 development.rb 中的更改之后启动应用程序服务器

这是输出：

=> Booting WEBrick
=> Rails 4.2.5 application starting in development on http://localhost:3000
=> Run `rails server -h` for more startup options
=> Ctrl-C to shutdown server
Exiting
/Users/adrian/workspace/learn-rails/config/environments/development.rb:67:in `block in <top (required)>': uninitialized constant ActiveSupport::EventedFileUpdateChecker (NameError)
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/railtie.rb:210:in `instance_eval'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/railtie.rb:210:in `configure'
from /Users/adrian/workspace/learn-rails/config/environments/development.rb:1:in `<top (required)>'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/engine.rb:598:in `block (2 levels) in <class:Engine>'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/engine.rb:597:in `each'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/engine.rb:597:in `block in <class:Engine>'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/initializable.rb:30:in `instance_exec'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/initializable.rb:30:in `run'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/initializable.rb:55:in `block in run_initializers'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:228:in `block in tsort_each'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:350:in `block (2 levels) in each_strongly_connected_component'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:422:in `block (2 levels) in each_strongly_connected_component_from'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:431:in `each_strongly_connected_component_from'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:421:in `block in each_strongly_connected_component_from'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/initializable.rb:44:in `each'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/initializable.rb:44:in `tsort_each_child'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:415:in `call'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:415:in `each_strongly_connected_component_from'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:349:in `block in each_strongly_connected_component'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:347:in `each'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:347:in `call'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:347:in `each_strongly_connected_component'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:226:in `tsort_each'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:205:in `tsort_each'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/initializable.rb:54:in `run_initializers'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/application.rb:352:in `initialize!'
from /Users/adrian/workspace/learn-rails/config/environment.rb:5:in `<top (required)>'
from /Users/adrian/workspace/learn-rails/config.ru:3:in `require_relative'
from /Users/adrian/workspace/learn-rails/config.ru:3:in `block in <main>'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/rack-1.6.4/lib/rack/builder.rb:55:in `instance_eval'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/rack-1.6.4/lib/rack/builder.rb:55:in `initialize'
from /Users/adrian/workspace/learn-rails/config.ru:in `new'
from /Users/adrian/workspace/learn-rails/config.ru:in `<main>'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/rack-1.6.4/lib/rack/builder.rb:49:in `eval'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/rack-1.6.4/lib/rack/builder.rb:49:in `new_from_string'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/rack-1.6.4/lib/rack/builder.rb:40:in `parse_file'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/rack-1.6.4/lib/rack/server.rb:299:in `build_app_and_options_from_config'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/rack-1.6.4/lib/rack/server.rb:208:in `app'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/commands/server.rb:61:in `app'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/rack-1.6.4/lib/rack/server.rb:336:in `wrapped_app'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/commands/server.rb:139:in `log_to_stdout'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/commands/server.rb:78:in `start'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:80:in `block in server'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:75:in `tap'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:75:in `server'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/commands.rb:17:in `<top (required)>'
from /Users/adrian/workspace/learn-rails/bin/rails:9:in `require'
from /Users/adrian/workspace/learn-rails/bin/rails:9:in `<top (required)>'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/spring-1.7.2/lib/spring/client/rails.rb:28:in `load'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/spring-1.7.2/lib/spring/client/rails.rb:28:in `call'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/spring-1.7.2/lib/spring/client/command.rb:7:in `call'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/spring-1.7.2/lib/spring/client.rb:30:in `run'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/spring-1.7.2/bin/spring:49:in `<top (required)>'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/spring-1.7.2/lib/spring/binstub.rb:11:in `load'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/spring-1.7.2/lib/spring/binstub.rb:11:in `<top (required)>'
from /Users/adrian/workspace/learn-rails/bin/spring:13:in `require'
from /Users/adrian/workspace/learn-rails/bin/spring:13:in `<top (required)>'
from bin/rails:3:in `load'
from bin/rails:3:in `<main>'

现在，我在提交之前做了很多研究，其他人也有类似的问题，例如 http://stackoverflow.com/questions/37796350/syntaxis-error-when-start-rails-server-after-first-configuration，但这些问题与 config/secrets.yml 文件的 ENV 错误有关。

我还看到了删除 development.rb 中以下行的建议：

 config.file_watcher = ActiveSupport::EventedFileUpdateChecker

但这似乎没有帮助，只给我以下错误消息：

Booting WEBrick
=> Rails 4.2.5 application starting in development on http://localhost:3000
=> Run `rails server -h` for more startup options
=> Ctrl-C to shutdown server
Exiting
/Users/adrian/workspace/learn-rails/config/initializers/new_framework_defaults.rb:15:in `<top (required)>': undefined method `to_time_preserves_timezone=' for ActiveSupport:Module (NoMethodError)
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:268:in `load'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:268:in `block in load'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:240:in `load_dependency'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:268:in `load'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/engine.rb:652:in `block in load_config_initializer'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/activesupport-4.2.5/lib/active_support/notifications.rb:166:in `instrument'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/engine.rb:651:in `load_config_initializer'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/engine.rb:616:in `block (2 levels) in <class:Engine>'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/engine.rb:615:in `each'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/engine.rb:615:in `block in <class:Engine>'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/initializable.rb:30:in `instance_exec'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/initializable.rb:30:in `run'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/initializable.rb:55:in `block in run_initializers'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:228:in `block in tsort_each'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:350:in `block (2 levels) in each_strongly_connected_component'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:422:in `block (2 levels) in each_strongly_connected_component_from'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:431:in `each_strongly_connected_component_from'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:421:in `block in each_strongly_connected_component_from'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/initializable.rb:44:in `each'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/initializable.rb:44:in `tsort_each_child'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:415:in `call'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:415:in `each_strongly_connected_component_from'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:349:in `block in each_strongly_connected_component'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:347:in `each'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:347:in `call'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:347:in `each_strongly_connected_component'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:226:in `tsort_each'
from /Users/adrian/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/tsort.rb:205:in `tsort_each'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/initializable.rb:54:in `run_initializers'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/application.rb:352:in `initialize!'
from /Users/adrian/workspace/learn-rails/config/environment.rb:5:in `<top (required)>'
from /Users/adrian/workspace/learn-rails/config.ru:3:in `require_relative'
from /Users/adrian/workspace/learn-rails/config.ru:3:in `block in <main>'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/rack-1.6.4/lib/rack/builder.rb:55:in `instance_eval'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/rack-1.6.4/lib/rack/builder.rb:55:in `initialize'
from /Users/adrian/workspace/learn-rails/config.ru:in `new'
from /Users/adrian/workspace/learn-rails/config.ru:in `<main>'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/rack-1.6.4/lib/rack/builder.rb:49:in `eval'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/rack-1.6.4/lib/rack/builder.rb:49:in `new_from_string'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/rack-1.6.4/lib/rack/builder.rb:40:in `parse_file'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/rack-1.6.4/lib/rack/server.rb:299:in `build_app_and_options_from_config'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/rack-1.6.4/lib/rack/server.rb:208:in `app'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/commands/server.rb:61:in `app'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/rack-1.6.4/lib/rack/server.rb:336:in `wrapped_app'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/commands/server.rb:139:in `log_to_stdout'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/commands/server.rb:78:in `start'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:80:in `block in server'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:75:in `tap'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:75:in `server'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/railties-4.2.5/lib/rails/commands.rb:17:in `<top (required)>'
from /Users/adrian/workspace/learn-rails/bin/rails:9:in `require'
from /Users/adrian/workspace/learn-rails/bin/rails:9:in `<top (required)>'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/spring-1.7.2/lib/spring/client/rails.rb:28:in `load'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/spring-1.7.2/lib/spring/client/rails.rb:28:in `call'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/spring-1.7.2/lib/spring/client/command.rb:7:in `call'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/spring-1.7.2/lib/spring/client.rb:30:in `run'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/spring-1.7.2/bin/spring:49:in `<top (required)>'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/spring-1.7.2/lib/spring/binstub.rb:11:in `load'
from /Users/adrian/.rvm/gems/ruby-2.3.1@learn-rails/gems/spring-1.7.2/lib/spring/binstub.rb:11:in `<top (required)>'
from /Users/adrian/workspace/learn-rails/bin/spring:13:in `require'
from /Users/adrian/workspace/learn-rails/bin/spring:13:in `<top (required)>'
from bin/rails:3:in `load'
from bin/rails:3:in `<main>'

这是我的 development.rb 文件的内容：

    Rails.application.configure do
  # Settings specified here will take precedence over those in config/application.rb.

  # In the development environment your application's code is reloaded on
  # every request. This slows down response time but is perfect for development
  # since you don't have to restart the web server when you make code changes.
  config.cache_classes = false

  # Do not eager load code on boot.
  config.eager_load = false

  # Show full error reports.
  config.consider_all_requests_local = true

  # Enable/disable caching. By default caching is disabled.
  if Rails.root.join('tmp/caching-dev.txt').exist?
    config.action_controller.perform_caching = true

    config.cache_store = :memory_store
    config.public_file_server.headers = {
      'Cache-Control' => 'public, max-age=172800'
    }
  else
    config.action_controller.perform_caching = false

    config.cache_store = :null_store
  end

  # Don't care if the mailer can't send.
  config.action_mailer.raise_delivery_errors = false

  config.action_mailer.perform_caching = false

  # Print deprecation notices to the Rails logger.
  config.active_support.deprecation = :log

  # Raise an error on page load if there are pending migrations.
  config.active_record.migration_error = :page_load

  # Debug mode disables concatenation and preprocessing of assets.
  # This option may cause significant delays in view rendering with a large
  # number of complex assets.
  config.assets.debug = true
  config.action_mailer.smtp_settings = {
   address: "smtp.sendgrid.net",
   port: 587,
   domain: Rails.application.secrets.domain_name,
   authentication: "plain",
   user_name: Rails.application.secrets.email_provider_username,
   password: Rails.application.secrets.email_provider_password
  }
  # ActionMailer Config
  config.action_mailer.default_url_options = { :host => 'localhost:3000' }
  config.action_mailer.delivery_method = :smtp
  config.action_mailer.raise_delivery_errors = true
  # Send email in development mode?
  config.action_mailer.perform_deliveries = true

  # Suppress logger output for asset requests.
  config.assets.quiet = true

  # Raises error for missing translations
  # config.action_view.raise_on_missing_translations = true

  # Use an evented file watcher to asynchronously detect changes in source code,
  # routes, locales, etc. This feature depends on the listen gem.
  config.file_watcher = ActiveSupport::EventedFileUpdateChecker
end

对此我感到非常沮丧，我正在按照教程进行操作并真正进入它。我真的很难过我做了什么来创建这个错误......

任何帮助将不胜感激！

编辑：我最终删除并重新开始了教程。这次我指定了我想要安装的确切版本（按照教程），而不是安装最新版本。

Answer 1

tl;dr：重新创建 Rails 项目，提供特定的 Rails 版本。

这通常是因为您安装的 Rails 版本比.railsrc 或template.rb 中要求的版本更新。

如果是这种情况，当您运行rails new my_new_app 时，该过程的早期步骤默认使用最新版本，但是一旦安装了模板/railsrc 版本，后面的步骤将使用此版本。这会导致兼容性问题。

您可以通过将rails -v（在您调用rails new 的目录中）的输出与.railsrc 或template.rb 中的内容进行比较来验证这是您的问题。如果它们不同，有一个简单的解决方法：

重新创建您的 Rails 应用，在命令行调用中指定与 .railsrc 或 template.rb 相同的 Rails 版本：
rails _4.2.5.1_ new my_new_app

Answer 2

您需要将listen gem 添加到您的Gemfile（最好在开发组中）并运行bundle install。