由于“未初始化的常量 Devise::Mailer”，Rails 服务器无法启动

【问题标题】：Rails server won't start due to "uninitialized constant Devise::Mailer"由于“未初始化的常量 Devise::Mailer”，Rails 服务器无法启动
【发布时间】：2017-01-11 10:29:01
【问题描述】：

在其他几篇文章中几乎没有提出其他解决方案，我确实按照他们的方式进行了操作，需要在 application.rb 文件中进行设计。我还重新安装了设计 gem 及其依赖项。尝试了几个小时后，我找不到解决方案，堆栈跟踪不断向我显示 Devise::Mailer 是一个带有 Nameerror 异常的未初始化常量。

我还安装了设计邀请 gem，但它并没有解决问题。 这实际上是在我安装 gem facets 并且我使用 rails 5 时开始的 下面你可以看看堆栈跟踪：

 usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.5/lib/active_support/inflector/methods.rb:263:in `const_get': uninitialized constant Devise::Mailer (NameError)
        from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.5/lib/active_support/inflector/methods.rb:263:in `block in constantize'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.5/lib/active_support/inflector/methods.rb:259:in `each'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.5/lib/active_support/inflector/methods.rb:259:in `inject'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.5/lib/active_support/inflector/methods.rb:259:in `constantize'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/devise-4.2.0/lib/devise.rb:301:in `get'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/devise-4.2.0/lib/devise.rb:320:in `mailer'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/devise_invitable-1.7.0/lib/devise_invitable/rails.rb:12:in `block in <class:Engine>'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.5/lib/active_support/callbacks.rb:446:in `instance_exec'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.5/lib/active_support/callbacks.rb:446:in `block in make_lambda'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.5/lib/active_support/callbacks.rb:192:in `block in simple'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.5/lib/active_support/callbacks.rb:504:in `block in call'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.5/lib/active_support/callbacks.rb:504:in `each'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.5/lib/active_support/callbacks.rb:504:in `call'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.5/lib/active_support/callbacks.rb:92:in `__run_callbacks__'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.5/lib/active_support/callbacks.rb:778:in `_run_prepare_callbacks'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/activesupport-4.2.5/lib/active_support/callbacks.rb:81:in `run_callbacks'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/actionpack-4.2.5/lib/action_dispatch/middleware/reloader.rb:83:in `prepare!'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/actionpack-4.2.5/lib/action_dispatch/middleware/reloader.rb:55:in `prepare!'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.5/lib/rails/application/finisher.rb:50:in `block in <module:Finisher>'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.5/lib/rails/initializable.rb:30:in `instance_exec'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.5/lib/rails/initializable.rb:30:in `run'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.5/lib/rails/initializable.rb:55:in `block in run_initializers'
        from /usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:228:in `block in tsort_each'
        from /usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:350:in `block (2 levels) in each_strongly_connected_component'
        from /usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:431:in `each_strongly_connected_component_from'
        from /usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:349:in `block in each_strongly_connected_component'
        from /usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:347:in `each'
        from /usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:347:in `call'
        from /usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:347:in `each_strongly_connected_component'
        from /usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:226:in `tsort_each'
        from /usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/tsort.rb:205:in `tsort_each'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.5/lib/rails/initializable.rb:54:in `run_initializers'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.5/lib/rails/application.rb:352:in `initialize!'
        from /home/ubuntu/workspace/config/environment.rb:5:in `<top (required)>'
        from /home/ubuntu/workspace/config.ru:3:in `block in <main>'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/rack-1.6.4/lib/rack/builder.rb:55:in `instance_eval'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/rack-1.6.4/lib/rack/builder.rb:55:in `initialize'
        from /home/ubuntu/workspace/config.ru:in `new'
        from /home/ubuntu/workspace/config.ru:in `<main>'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/rack-1.6.4/lib/rack/builder.rb:49:in `eval'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/rack-1.6.4/lib/rack/builder.rb:49:in `new_from_string'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/rack-1.6.4/lib/rack/builder.rb:40:in `parse_file'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/rack-1.6.4/lib/rack/server.rb:299:in `build_app_and_options_from_config'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/rack-1.6.4/lib/rack/server.rb:208:in `app'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.5/lib/rails/commands/server.rb:61:in `app'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/rack-1.6.4/lib/rack/server.rb:336:in `wrapped_app'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.5/lib/rails/commands/server.rb:139:in `log_to_stdout'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.5/lib/rails/commands/server.rb:78:in `start'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:80:in `block in server'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:75:in `tap'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:75:in `server'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/railties-4.2.5/lib/rails/commands.rb:17:in `<top (required)>'
        from /home/ubuntu/workspace/bin/rails:9:in `require'
        from /home/ubuntu/workspace/bin/rails:9:in `<top (required)>'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/spring-1.7.2/lib/spring/client/rails.rb:28:in `load'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/spring-1.7.2/lib/spring/client/rails.rb:28:in `call'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/spring-1.7.2/lib/spring/client/command.rb:7:in `call'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/spring-1.7.2/lib/spring/client.rb:30:in `run'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/spring-1.7.2/bin/spring:49:in `<top (required)>'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/spring-1.7.2/lib/spring/binstub.rb:11:in `load'
        from /usr/local/rvm/gems/ruby-2.3.0/gems/spring-1.7.2/lib/spring/binstub.rb:11:in `<top (required)>'
        from /home/ubuntu/workspace/bin/spring:13:in `require'
        from /home/ubuntu/workspace/bin/spring:13:in `<top (required)>'
        from bin/rails:3:in `load'
        from bin/rails:3:in `<main>'

【问题讨论】：

  • 我在添加 facets gem 后遇到了同样的错误。唯一改变的是添加宝石，甚至不需要任何东西。你找到解决办法了吗？

标签： ruby-on-rails ruby devise rubygems


【解决方案1】：

确保您已将此代码放置在您正在使用的环境中。因此，如果您在开发服务器中使用它，则需要转到 config --> development.rb 并插入此代码。 config.action_mailer.default_url_options = { host: 'localhost', port: 3000 }

有关更多信息，请参阅指南：http://devise.plataformatec.com.br/#getting-started

【讨论】：

    【解决方案2】：

    执行以下操作：

    rails g devise:install

    那么，execute rails db:migrate

    按照https://github.com/plataformatec/devise上的步骤了解更多详情

    确保在此之后重新启动服务器

    【讨论】：

    • 忘了提到已经安装了设计并执行了迁移，但我得到了堆栈跟踪和错误
    • 在 development.rb 中添加邮件设置以发送邮件
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