在其他几篇文章中提出了很少其他解决方案，我确实按照它们进行了操作，需要在application.rb文件中进行设计。我还重新安装了devise gem及其依赖项。在尝试了几个小时之后，我无法找到解决方案，并且堆栈跟踪继续向我显示 Devise :: Mailer是一个未初始化的常量，带有Nameerror异常。
我还安装了设计邀请宝石，但它没有解决问题。 这实际上是在我安装宝石刻面时开始的，而我正在使用rails 5 下面你可以看一下堆栈跟踪：
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>'
答案 0 :(得分：0)
执行以下操作：
rails g devise:install
然后，execute rails db:migrate
按照https://github.com/plataformatec/devise上的步骤了解详情
确保在此之后重新启动服务器
答案 1 :(得分：0)
确保已将此代码放在您正在使用的环境中。因此，如果您在开发服务器中使用此功能，则需要转到config - ＆gt; development.rb并插入此代码。
config.action_mailer.default_url_options = { host: 'localhost', port: 3000 }
有关详细信息，请参阅指南：http://devise.plataformatec.com.br/#getting-started