ruby-on-rails - Rails的错误:`method_missing':未定义的方法`active_record'

Question

我的rails项目以前可以工作。我收到此错误，是因为我删除了mysql及其相关的所有内容。

然后我重新安装了mysql。收到此错误。然后，我重新安装了ruby和rails。错误仍然存​​在。使用“rails new myapp”，
然后是“捆绑安装”
然后是“rails s”，

我收到以下错误:

=> Booting WEBrick
=> Rails 4.0.2 application starting in development on 

=> Run `rails server -h` for more startup options
=> Ctrl-C to shutdown server
Exiting
**/home/cwu/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/railtie/configuration.rb:95:in `method_missing': undefined method `active_record' for #<Rails::Application::Configuration:0x0000000303cae8> (NoMethodError)
    from /home/cwu/Dropbox/project/web/atop/config/environments/development.rb:23:in `block in <top (required)>'**
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/railtie/configurable.rb:24:in `class_eval'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/railtie/configurable.rb:24:in `configure'
    from /home/cwu/Dropbox/project/web/atop/config/environments/development.rb:1:in `<top (required)>'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/activesupport-4.0.2/lib/active_support/dependencies.rb:229:in `require'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/activesupport-4.0.2/lib/active_support/dependencies.rb:229:in `block in require'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/activesupport-4.0.2/lib/active_support/dependencies.rb:214:in `load_dependency'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/activesupport-4.0.2/lib/active_support/dependencies.rb:229:in `require'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/engine.rb:591:in `block (2 levels) in <class:Engine>'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/engine.rb:590:in `each'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/engine.rb:590:in `block in <class:Engine>'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/initializable.rb:30:in `instance_exec'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/initializable.rb:30:in `run'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/initializable.rb:55:in `block in run_initializers'
    from /home/cwu/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/tsort.rb:226:in `block in tsort_each'
    from /home/cwu/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/tsort.rb:348:in `block (2 levels) in each_strongly_connected_component'
    from /home/cwu/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/tsort.rb:418:in `block (2 levels) in each_strongly_connected_component_from'
    from /home/cwu/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/tsort.rb:427:in `each_strongly_connected_component_from'
    from /home/cwu/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/tsort.rb:417:in `block in each_strongly_connected_component_from'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/initializable.rb:44:in `each'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/initializable.rb:44:in `tsort_each_child'
    from /home/cwu/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/tsort.rb:411:in `call'
    from /home/cwu/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/tsort.rb:411:in `each_strongly_connected_component_from'
    from /home/cwu/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/tsort.rb:347:in `block in each_strongly_connected_component'
    from /home/cwu/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/tsort.rb:345:in `each'
    from /home/cwu/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/tsort.rb:345:in `call'
    from /home/cwu/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/tsort.rb:345:in `each_strongly_connected_component'
    from /home/cwu/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/tsort.rb:224:in `tsort_each'
    from /home/cwu/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/tsort.rb:205:in `tsort_each'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/initializable.rb:54:in `run_initializers'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/application.rb:215:in `initialize!'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/railtie/configurable.rb:30:in `method_missing'
    from /home/cwu/Dropbox/project/web/atop/config/environment.rb:5:in `<top (required)>'
    from /home/cwu/Dropbox/project/web/atop/config.ru:3:in `require'
    from /home/cwu/Dropbox/project/web/atop/config.ru:3:in `block in <main>'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/rack-1.5.2/lib/rack/builder.rb:55:in `instance_eval'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/rack-1.5.2/lib/rack/builder.rb:55:in `initialize'
    from /home/cwu/Dropbox/project/web/atop/config.ru:in `new'
    from /home/cwu/Dropbox/project/web/atop/config.ru:in `<main>'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/rack-1.5.2/lib/rack/builder.rb:49:in `eval'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/rack-1.5.2/lib/rack/builder.rb:49:in `new_from_string'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/rack-1.5.2/lib/rack/builder.rb:40:in `parse_file'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/rack-1.5.2/lib/rack/server.rb:277:in `build_app_and_options_from_config'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/rack-1.5.2/lib/rack/server.rb:199:in `app'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/commands/server.rb:48:in `app'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/rack-1.5.2/lib/rack/server.rb:314:in `wrapped_app'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/commands/server.rb:75:in `start'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/commands.rb:76:in `block in <top (required)>'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/commands.rb:71:in `tap'
    from /home/cwu/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/commands.rb:71:in `<top (required)>'
    from bin/rails:4:in `require'
    from bin/rails:4:in `<main>'

Answer 1

该错误很明显，即在config/environments/development.rb:23中配置了未加载的active_record。

只需删除

config.active_record.migration_error = :page_load

会好的。