设置 Rails 应用程序时出现问题。它第一次工作，但后来当我重新打开它并尝试运行“rails 服务器”时，它不起作用并返回以下错误。 谢谢。
我使用的是 ruby 2.3.1p112 导轨5.0 mysql 5.7.13 $ Rails 服务器
=> 启动 Puma
=> Rails 5.0.0 应用程序开始在 http://localhost:3000 上开发
=> 运行
rails server -h/Users/bruce/sea/config/routes.rb:6:在`
main:Object 的方法“root”（NoMethodError）
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/activesupport-
5.0.0/lib/active_support/dependency.rb:287:在“加载”中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/activesupport-
5.0.0/lib/active_support/dependency.rb:287:在“加载中的块”中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/activesupport-
5.0.0/lib/active_support/dependency.rb:259:在`load_dependency'中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/activesupport-
5.0.0/lib/active_support/dependency.rb:287:在“加载”中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/railties-5.0.0/lib
/rails/application/routes_reloader.rb:40:在“load_paths 中的块”中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/railties-5.0.0/lib
/rails/application/routes_reloader.rb:40:在“每个”中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/railties-5.0.0/lib
/rails/application/routes_reloader.rb:40:在`load_paths'中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/railties-5.0.0/lib
/rails/application/routes_reloader.rb:16:在“重新加载！”中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/railties-5.0.0/lib
/rails/application/routes_reloader.rb:26:在“更新程序中的块”中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/activesupport-
5.0.0/lib/active_support/file_update_checker.rb:77:在“执行”中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/railties-5.0.0/lib
/rails/application/routes_reloader.rb:27:在“更新程序”中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/railties-5.0.0/lib
/rails/application/routes_reloader.rb:7:在`execute_if_updated'中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/railties-5.0.0/lib
/rails/application/finisher.rb:119:在`模块中的块：Finisher'
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/railties-5.0.0/lib
/rails/initialized.rb:30:在`instance_exec'中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/railties-5.0.0/lib
/rails/initialized.rb:30:在“运行”中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/railties-5.0.0/lib
/rails/initialized.rb:55:在 `run_initializers 中的块'
from /Users/bruce/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0
/tsort.rb:228:in `tsort_each 中的块'
from /Users/bruce/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0
/tsort.rb:350:in `each_strongly_connected_component' 中的块（2 级）
from /Users/bruce/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0
/tsort.rb：431：在“each_strongly_connected_component_from”中
from /Users/bruce/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0
/tsort.rb:349:in `each_strongly_connected_component 中的块'
from /Users/bruce/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0
/tsort.rb:347:在“每个”中
from /Users/bruce/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0
/tsort.rb:347:在“调用”中
from /Users/bruce/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0
/tsort.rb:347:在`each_strongly_connected_component'中
from /Users/bruce/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0
/tsort.rb:226:在`tsort_each'中
from /Users/bruce/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0
/tsort.rb:205:在`tsort_each'中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/railties-5.0.0/lib
/rails/initialized.rb:54:在`run_initializers'中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/railties-5.0.0/lib
/rails/application.rb:352:在`初始化！'
from /Users/bruce/sea/config/environment.rb:5:in `<top (required)>'
from /Users/bruce/sea/config.ru:3:in `require_relative'
from /Users/bruce/sea/config.ru:3:in `block in <main>'
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/rack-2.0.1/lib
/rack/builder.rb:55:在`instance_eval'中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/rack-2.0.1/lib
/rack/builder.rb:55:在`初始化'
from /Users/bruce/sea/config.ru:in `new'
from /Users/bruce/sea/config.ru:in `<main>'
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/rack-2.0.1/lib
/rack/builder.rb:49:在“评估”中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/rack-2.0.1/lib
/rack/builder.rb:49:在`new_from_string'中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/rack-2.0.1/lib
/rack/builder.rb:40:在`parse_file'中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/rack-2.0.1/lib
/rack/server.rb:318:在`build_app_and_options_from_config'中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/rack-2.0.1/lib
/rack/server.rb:218:在“应用程序”中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/railties-5.0.0/lib
/rails/commands/server.rb:59:在“应用程序”中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/rack-2.0.1/lib
/rack/server.rb:353:在`wrapped_app'中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/railties-5.0.0/lib
/rails/commands/server.rb:124:在`log_to_stdout'中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/railties-5.0.0/lib
/rails/commands/server.rb:77:在`开始'
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/railties-5.0.0/lib
/rails/commands/commands_tasks.rb:90:在`服务器中的块'中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/railties-5.0.0/lib
/rails/commands/commands_tasks.rb:85:在“点击”中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/railties-5.0.0/lib
/rails/commands/commands_tasks.rb:85:在“服务器”中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/railties-5.0.0/lib
/rails/commands/commands_tasks.rb：49：在“run_command！”中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/railties-5.0.0/lib
/rails/commands.rb:18:in `
from /Users/bruce/sea/bin/rails:9:in `require'
from /Users/bruce/sea/bin/rails:9:in `<top (required)>'
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/spring-1.7.2/lib
/spring/client/rails.rb:28:在“加载”中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/spring-1.7.2/lib
/spring/client/rails.rb:28:在“调用”中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/spring-1.7.2/lib
/spring/client/command.rb:7:在`call'中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/spring-1.7.2/lib
/spring/client.rb:30:在“运行”中
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/spring-1.7.2/bin
/春天：49：在`
from /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/spring-1.7.2/lib
/spring/binstub.rb:11:在“加载”中
来自 /Users/bruce/.rvm/gems/ruby-2.3.1@global/gems/spring-1.7.2/lib
/spring/binstub.rb:11:在`
from /Users/bruce/sea/bin/spring:13:in `require'
from /Users/bruce/sea/bin/spring:13:in `<top (required)>'
from bin/rails:3:in `load'`enter
from bin/rails:3:in `<main>'
似乎在你的routes.rb文件中你错误地拥有了
rootroot_url希望这对您有帮助。