Rails serverを立ち上げようとしたが、Nameエラーが発生

Question

前提・実現したいこと

Rails serverコマンドを実行後に出力される、Name errorを改善したいのですが、改善方法がわかりません。
学習が進められないので、教えていただけると幸いです。

発生している問題・エラーメッセージ

Puma caught this error: uninitialized constant ActionController::Baseincuku (NameError)

該当のソースコード

$rails s

=> Booting Puma
=> Rails 6.0.3 application starting in development
=> Run rails server --help for more startup options
[18021] Puma starting in cluster mode...
[18021] * Version 4.3.6 (ruby 2.6.3-p62), codename: Mysterious Traveller
[18021] * Min threads: 5, max threads: 5
[18021] * Environment: development
[18021] * Process workers: 2
[18021] * Preloading application
[18021] * Listening on tcp://127.0.0.1:8080
[18021] * Listening on tcp://[::1]:8080
[18021] Use Ctrl-C to stop
[18021] - Worker 0 (pid: 18070) booted, phase: 0
[18021] - Worker 1 (pid: 18071) booted, phase: 0
2021-07-21 08:24:52 +0000: Rack app error handling request { GET / }
<NameError: uninitialized constant ActionController::Baseincuku>
/home/ubuntu/environment/sample_app/app/controllers/application_controller.rb:1:in <main>' /home/ubuntu/.rvm/gems/ruby-2.6.3/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in require'
/home/ubuntu/.rvm/gems/ruby-2.6.3/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in block in require_with_bootsnap_lfi' /home/ubuntu/.rvm/gems/ruby-2.6.3/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/loaded_features_index.rb:92:in register'
/home/ubuntu/.rvm/gems/ruby-2.6.3/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:21:in require_with_bootsnap_lfi' /home/ubuntu/.rvm/gems/ruby-2.6.3/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:30:in require'
/home/ubuntu/.rvm/gems/ruby-2.6.3/gems/zeitwerk-2.4.2/lib/zeitwerk/kernel.rb:26:in require' /home/ubuntu/.rvm/gems/ruby-2.6.3/gems/actiontext-6.0.3/lib/action_text/engine.rb:47:in block (2 levels) in class:Engine'
/home/ubuntu/.rvm/gems/ruby-2.6.3/gems/activesupport-6.0.3/lib/active_support/callbacks.rb:428:in instance_exec' /home/ubuntu/.rvm/gems/ruby-2.6.3/gems/activesupport-6.0.3/lib/active_support/callbacks.rb:428:in block in make_lambda'
/home/ubuntu/.rvm/gems/ruby-2.6.3/gems/activesupport-6.0.3/lib/active_support/callbacks.rb:200:in block (2 levels) in halting' /home/ubuntu/.rvm/gems/ruby-2.6.3/gems/activesupport-6.0.3/lib/active_support/callbacks.rb:605:in block (2 levels) in default_terminator'
/home/ubuntu/.rvm/gems/ruby-2.6.3/gems/activesupport-6.0.3/lib/active_support/callbacks.rb:604:in catch' /home/ubuntu/.rvm/gems/ruby-2.6.3/gems/activesupport-6.0.3/lib/active_support/callbacks.rb:604:in block in default_terminator'
/home/ubuntu/.rvm/gems/ruby-2.6.3/gems/activesupport-6.0.3/lib/active_support/callbacks.rb:201:in block in halting' /home/ubuntu/.rvm/gems/ruby-2.6.3/gems/activesupport-6.0.3/lib/active_support/callbacks.rb:513:in block in invoke_before'
/home/ubuntu/.rvm/gems/ruby-2.6.3/gems/activesupport-6.0.3/lib/active_support/callbacks.rb:513:in each' /home/ubuntu/.rvm/gems/ruby-2.6.3/gems/activesupport-6.0.3/lib/active_support/callbacks.rb:513:in invoke_before'
/home/ubuntu/.rvm/gems/ruby-2.6.3/gems/activesupport-6.0.3/lib/active_support/callbacks.rb:134:in run_callbacks' /home/ubuntu/.rvm/gems/ruby-2.6.3/gems/activesupport-6.0.3/lib/active_support/execution_wrapper.rb:119:in complete!'
/home/ubuntu/.rvm/gems/ruby-2.6.3/gems/activesupport-6.0.3/lib/active_support/execution_wrapper.rb:76:in ensure in block in run!' /home/ubuntu/.rvm/gems/ruby-2.6.3/gems/activesupport-6.0.3/lib/active_support/execution_wrapper.rb:76:in block in run!'
/home/ubuntu/.rvm/gems/ruby-2.6.3/gems/activesupport-6.0.3/lib/active_support/execution_wrapper.rb:70:in tap' /home/ubuntu/.rvm/gems/ruby-2.6.3/gems/activesupport-6.0.3/lib/active_support/execution_wrapper.rb:70:in run!'
/home/ubuntu/.rvm/gems/ruby-2.6.3/gems/actionpack-6.0.3/lib/action_dispatch/middleware/executor.rb:12:in call' /home/ubuntu/.rvm/gems/ruby-2.6.3/gems/actionpack-6.0.3/lib/action_dispatch/middleware/static.rb:126:in call'
/home/ubuntu/.rvm/gems/ruby-2.6.3/gems/rack-2.2.3/lib/rack/sendfile.rb:110:in call' /home/ubuntu/.rvm/gems/ruby-2.6.3/gems/actionpack-6.0.3/lib/action_dispatch/middleware/host_authorization.rb:76:in call'
/home/ubuntu/.rvm/gems/ruby-2.6.3/gems/webpacker-4.0.7/lib/webpacker/dev_server_proxy.rb:29:in perform_request' /home/ubuntu/.rvm/gems/ruby-2.6.3/gems/rack-proxy-0.7.0/lib/rack/proxy.rb:63:in call'
/home/ubuntu/.rvm/gems/ruby-2.6.3/gems/railties-6.0.3/lib/rails/engine.rb:527:in call' /home/ubuntu/.rvm/gems/ruby-2.6.3/gems/puma-4.3.6/lib/puma/configuration.rb:228:in call'
/home/ubuntu/.rvm/gems/ruby-2.6.3/gems/puma-4.3.6/lib/puma/server.rb:713:in handle_request' /home/ubuntu/.rvm/gems/ruby-2.6.3/gems/puma-4.3.6/lib/puma/server.rb:472:in process_client'
/home/ubuntu/.rvm/gems/ruby-2.6.3/gems/puma-4.3.6/lib/puma/server.rb:328:in block in run' /home/ubuntu/.rvm/gems/ruby-2.6.3/gems/puma-4.3.6/lib/puma/thread_pool.rb:134:in block in spawn_thread'

Comments

[winterboum]

取り敢えず
app/controllers/application_controller.rb:

を載せてください

Answer 1

uninitialized constant ActionController::Baseincuku というエラーメッセージは、ActionController::Baseincukuという未定義の定数がある、という意味です。

Rubyの場合、定数は大文字で始まるもので、普通の定数の他にもクラス名やモジュール名も定数になります。

そして /home/ubuntu/environment/sample_app/app/controllers/application_controller.rb:1: というメッセージから、app/controllers/application_controller.rb の1行目に問題がありそうです。

おそらく、 ActionController::Baseとなるべきところに誤って文字列がつながってしまって、 ActionController::Baseincuku か何かになっているのではないでしょうか？