未建立连接 - Ruby on Rails

Question

我是 Ruby on Rails 的新手，我正在试一试。 我提前说我没有找到适合我的问题的答案，也没有在 StackOverflow 和互联网上找到答案（我尝试了从 SO 和其他网站挑选的许多不同的东西）。

我在 CodeSchool 上关注 Rails for Zombies 2，我需要设置环境以使事情发生。

为了做到这一点，我正在遵循 Michael Hartl 的设置阶段 Ruby on Rails 教程。

我遵循了每一步，但是，当我想在浏览器中看到：“hello, world!”时，我得到：

ActiveRecord::ConnectionNotEstablished

No connection pool for ActiveRecord::Base

完整跟踪：

activerecord (4.2.2) lib/active_record/connection_adapters/abstract/connection_pool.rb:566:in `retrieve_connection'
activerecord (4.2.2) lib/active_record/connection_handling.rb:113:in `retrieve_connection'
activerecord (4.2.2) lib/active_record/connection_handling.rb:87:in `connection'
activerecord (4.2.2) lib/active_record/query_cache.rb:51:in `restore_query_cache_settings'
activerecord (4.2.2) lib/active_record/query_cache.rb:43:in `rescue in call'
activerecord (4.2.2) lib/active_record/query_cache.rb:31:in `call'
activerecord (4.2.2) lib/active_record/connection_adapters/abstract/connection_pool.rb:649:in `call'
actionpack (4.2.2) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
activesupport (4.2.2) lib/active_support/callbacks.rb:88:in `call'
activesupport (4.2.2) lib/active_support/callbacks.rb:88:in `_run_callbacks'
activesupport (4.2.2) lib/active_support/callbacks.rb:776:in `_run_call_callbacks'
activesupport (4.2.2) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (4.2.2) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (4.2.2) lib/action_dispatch/middleware/reloader.rb:73:in `call'
actionpack (4.2.2) lib/action_dispatch/middleware/remote_ip.rb:78:in `call'
web-console (2.0.0.beta3) lib/action_dispatch/debug_exceptions.rb:18:in `middleware_call'
web-console (2.0.0.beta3) lib/action_dispatch/debug_exceptions.rb:13:in `call'
actionpack (4.2.2) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
railties (4.2.2) lib/rails/rack/logger.rb:38:in `call_app'
railties (4.2.2) lib/rails/rack/logger.rb:20:in `block in call'
activesupport (4.2.2) lib/active_support/tagged_logging.rb:68:in `block in tagged'
activesupport (4.2.2) lib/active_support/tagged_logging.rb:26:in `tagged'
activesupport (4.2.2) lib/active_support/tagged_logging.rb:68:in `tagged'
railties (4.2.2) lib/rails/rack/logger.rb:20:in `call'
actionpack (4.2.2) lib/action_dispatch/middleware/request_id.rb:21:in `call'
rack (1.6.4) lib/rack/methodoverride.rb:22:in `call'
rack (1.6.4) lib/rack/runtime.rb:18:in `call'
activesupport (4.2.2) lib/active_support/cache/strategy/local_cache_middleware.rb:28:in `call'
rack (1.6.4) lib/rack/lock.rb:17:in `call'
actionpack (4.2.2) lib/action_dispatch/middleware/static.rb:113:in `call'
rack (1.6.4) lib/rack/sendfile.rb:113:in `call'
railties (4.2.2) lib/rails/engine.rb:518:in `call'
railties (4.2.2) lib/rails/application.rb:164:in `call'
rack (1.6.4) lib/rack/lock.rb:17:in `call'
rack (1.6.4) lib/rack/content_length.rb:15:in `call'
rack (1.6.4) lib/rack/handler/webrick.rb:88:in `service'

在得到这个之前，我安装了 Rails，我进入了我的 hello_app 文件夹并使用了：Bundle Install，然后我只使用了：Rails Server。我还按照指南中的说明删除了 index.html。

我的 Gemfile：

source 'https://rubygems.org'

gem 'rails',                '4.2.2'
gem 'sass-rails',           '5.0.2'
gem 'uglifier',             '2.5.3'
gem 'coffee-rails',         '4.1.0'
gem 'jquery-rails',         '>= 3.0.0'
gem 'turbolinks',           '2.3.0'
gem 'jbuilder',             '2.2.3'
gem 'sdoc',                 '0.4.0', group: :doc

group :development, :test do
  gem 'sqlite3'
  gem 'pry-byebug', platform: [:ruby_20]
  gem 'web-console', '2.0.0.beta3'
  gem 'spring',      '1.1.3'
end

我的应用程序控制器：

class ApplicationController < ActionController::Base
      protect_from_forgery with: :exception

      def hello
        render text: "hello, world!"
      end
end

我的路线：

HelloApp::Application.routes.draw do
        root 'application#hello
end

我的数据库：

development:
  adapter: sqlite3
  database: db/development.sqlite3
  pool: 5
  timeout: 5000

test:
  adapter: sqlite3
  database: db/test.sqlite3
  pool: 5
  timeout: 5000

production:
  adapter: sqlite3
  database: db/production.sqlite3
  pool: 5
  timeout: 5000

如果我的问题是微不足道的，我很抱歉，我也为我糟糕的英语感到抱歉。

提前谢谢你！

Answer 1

顺便说一句，您是否在启动服务器之前运行了bundle exec rake db:setup？看起来您的数据库还不存在（您可以检查db/development.sqlite3 文件是否存在）。

Answer 2

我自己解决了。这是由损坏的 Gemfile 引起的问题。 允许我让它工作的正确配置是：

宝石文件：

source 'https://rubygems.org'


# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
 gem 'rails', '4.2.2'
# Use sqlite3 as the database for Active Record
 gem 'sqlite3'
# 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 following links in your web application faster.   Read more: https://github.com/rails/turbolinks
 gem 'turbolinks'
# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
 gem 'jbuilder', '~> 2.0'
# bundle exec rake doc:rails generates the API under doc/api.
 gem 'sdoc', '~> 0.4.0', group: :doc

# Use ActiveModel has_secure_password
# gem 'bcrypt', '~> 3.1.7'

# Use Unicorn as the app server
# gem 'unicorn'

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

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

# Access an IRB console on exception pages or by using <%= console %> in views
   gem 'web-console', '~> 2.0'

# Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
   gem 'spring'
 end