Question

我是Ruby on Rails的新手。运行'bundle'命令进行更新/安装后，当我尝试rails s或rails g mongoid:config控制台返回此消息时，该消息以：

开头

/home/myUser/proyect/config/environments/development.rb:50:in `block in <top (required)>': uninitialized constant ActiveSupport::EventedFileUpdateChecker (NameError)

这是我的Gemfile（是的，我想使用MongoDB作为数据库）：

source 'https://rubygems.org'


# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '4.2.6'
# Use sqlite3 as the database for Active Record
gem 'sqlite3'
# Use Mongoid as the database
gem 'mongoid', '~> 5.1.0'
# Use bson
gem 'bson_ext'
# Use Puma as the app server
gem 'puma', '~> 3.0'
#Use Haml for html
gem 'haml'
# Use SCSS for stylesheets
gem 'sass-rails', '~> 5.0'
# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'
# Use CoffeeScript for .coffee assets and views
gem 'coffee-rails', '~> 4.1.0'
# See https://github.com/rails/execjs#readme for more supported runtimes
# gem 'therubyracer', platforms: :ruby

# Use jquery as the JavaScript library
gem 'jquery-rails'
# Turbolinks makes navigating your web application faster. Read more: https://github.com/turbolinks/turbolinks
gem 'turbolinks', '~> 5.x'
# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem 'jbuilder', '~> 2.0'
# Use Redis adapter to run Action Cable in production
# gem 'redis', '~> 3.0'
# Use ActiveModel has_secure_password
# gem 'bcrypt', '~> 3.1.7'

# Use Capistrano for deployment
# gem 'capistrano-rails', group: :development

group :development, :test do
  # Call 'byebug' anywhere in the code to stop execution and get a debugger console
  gem 'byebug', platform: :mri
end

group :development do
  # Access an IRB console on exception pages or by using <%= console %> anywhere in the code.
  gem 'web-console'
  gem 'listen', '~> 3.0.5'
  # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
  gem 'spring'
  gem 'spring-watcher-listen', '~> 2.0.0'
end

# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]

config / environments / development.rb 文件：

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

  # 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

Answer 1

根据Rails changelogs，config.file_watcher中引入了Rails 5选项。它允许您根据文件更改进行自动重新加载。此功能取决于listener gem，并且您已在gemfile中列出它。但对我来说可疑的是你的Rails版本！

gem 'rails', '4.2.6'
# but rails 4 does not support that feature!

看起来您已经从另一个版本的development.rb框架，另一个项目中复制了Gemfile（或Rails配置？），或者手动将您的gemfile版本更改为不适当的状态。

我可以建议你的两个选择：

要将rails gemfile版本更改为最新版本，如下所示：
```
gem 'rails', github: 'rails/rails'
```
再次bundle;
从配置文件中删除config.file_watcher行。

Answer 2

tl; dr：重新创建您的Rails项目，提供特定的Rails版本。

通常会发生这种情况，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，默认情况下会使用最新版本来处理该过程的早期步骤，但是一旦安装了模板/ railsrc版本，后面的步骤就会使用此版本。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{{{{}}中的内容进行比较来验证这是您的问题。 1}}。如果它们不同，可以轻松解决：

重新创建您的Rails应用，在命令行调用中从template.rb或.railsrc指定相同的Rails版本：
template.rb

Answer 3

如果您删除config.file_watcher = ActiveSupport::EventedFileUpdateChecker，它将有效。它检测源代码中的变化以异步刷新，但它也取决于listen gem，因为您是初学者，它只会给您带来麻烦。应该没有它。

env配置文件中未初始化的常量ActiveSupport :: EventedFileUpdateChecker

3 个答案:

tl; dr：重新创建您的Rails项目，提供特定的Rails版本。