レーキが中止！未定義のメソッド `each 'for nil：capstone ptourist appのNilClass

Question

' heroku run rake ptourist：reset_all --remote staging 'コマンドを実行するたびにこのエラーが発生します。 質問に適切に答えるためにさらに情報が必要な場合はお知らせください。 フル・トレース：あなたのテーブルの外部キーの値が空のデータが含まれている場合

rake aborted! 
NoMethodError: undefined method `each' for nil:NilClass 
/app/vendor/bundle/ruby/2.2.0/gems/mongo-2.4.1/lib/mongo/cluster.rb:167:in `initialize' 
/app/vendor/bundle/ruby/2.2.0/gems/mongo-2.4.1/lib/mongo/client.rb:370:in `new' 
/app/vendor/bundle/ruby/2.2.0/gems/mongo-2.4.1/lib/mongo/client.rb:370:in `create_from_addresses' 
/app/vendor/bundle/ruby/2.2.0/gems/mongo-2.4.1/lib/mongo/client.rb:235:in `initialize' 
/app/vendor/bundle/ruby/2.2.0/gems/mongoid-5.2.0/lib/mongoid/clients/factory.rb:64:in `new' 
/app/vendor/bundle/ruby/2.2.0/gems/mongoid-5.2.0/lib/mongoid/clients/factory.rb:64:in `create_client' 
/app/vendor/bundle/ruby/2.2.0/gems/mongoid-5.2.0/lib/mongoid/clients/factory.rb:42:in `default' 
/app/vendor/bundle/ruby/2.2.0/gems/mongoid-5.2.0/lib/mongoid/clients.rb:38:in `default' 
/app/vendor/bundle/ruby/2.2.0/gems/database_cleaner-1.5.3/lib/database_cleaner/mongo2/truncation_mixin.rb:18:in `database' 
/app/vendor/bundle/ruby/2.2.0/gems/database_cleaner-1.5.3/lib/database_cleaner/mongo2/truncation_mixin.rb:29:in `collections' 
/app/vendor/bundle/ruby/2.2.0/gems/database_cleaner-1.5.3/lib/database_cleaner/mongo2/truncation_mixin.rb:9:in `clean' 
/app/vendor/bundle/ruby/2.2.0/gems/database_cleaner-1.5.3/lib/database_cleaner/base.rb:46:in `clean_with' 
/app/lib/tasks/ptourist.rake:101:in `block (2 levels) in <top (required)>' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/task.rb:250:in `call' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/task.rb:250:in `block in execute' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/task.rb:250:in `each' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/task.rb:250:in `execute' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/task.rb:194:in `block in invoke_with_call_chain' 
/app/vendor/ruby-2.2.6/lib/ruby/2.2.0/monitor.rb:211:in `mon_synchronize' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/task.rb:187:in `invoke_with_call_chain' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/task.rb:216:in `block in invoke_prerequisites' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/task.rb:214:in `each' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/task.rb:214:in `invoke_prerequisites' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/task.rb:193:in `block in invoke_with_call_chain' 
/app/vendor/ruby-2.2.6/lib/ruby/2.2.0/monitor.rb:211:in `mon_synchronize' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/task.rb:187:in `invoke_with_call_chain' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/task.rb:216:in `block in invoke_prerequisites' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/task.rb:214:in `each' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/task.rb:214:in `invoke_prerequisites' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/task.rb:193:in `block in invoke_with_call_chain' 
/app/vendor/ruby-2.2.6/lib/ruby/2.2.0/monitor.rb:211:in `mon_synchronize' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/task.rb:187:in `invoke_with_call_chain' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/task.rb:216:in `block in invoke_prerequisites' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/task.rb:214:in `each' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/task.rb:214:in `invoke_prerequisites' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/task.rb:193:in `block in invoke_with_call_chain' 
/app/vendor/ruby-2.2.6/lib/ruby/2.2.0/monitor.rb:211:in `mon_synchronize' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/task.rb:187:in `invoke_with_call_chain' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/task.rb:180:in `invoke' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/application.rb:152:in `invoke_task' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/application.rb:108:in `block (2 levels) in top_level' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/application.rb:108:in `each' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/application.rb:108:in `block in top_level' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/application.rb:117:in `run_with_threads' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/application.rb:102:in `top_level' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/application.rb:80:in `block in run' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/application.rb:178:in `standard_exception_handling' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/lib/rake/application.rb:77:in `run' 
/app/vendor/bundle/ruby/2.2.0/gems/rake-12.0.0/exe/rake:27:in `<top (required)>' 
/app/vendor/bundle/ruby/2.2.0/bin/rake:23:in `load' 
/app/vendor/bundle/ruby/2.2.0/bin/rake:23:in `<top (required)>' 
/app/vendor/bundle/ruby/2.2.0/gems/bundler-1.13.7/lib/bundler/cli/exec.rb:74:in `load' 
/app/vendor/bundle/ruby/2.2.0/gems/bundler-1.13.7/lib/bundler/cli/exec.rb:74:in `kernel_load' 
/app/vendor/bundle/ruby/2.2.0/gems/bundler-1.13.7/lib/bundler/cli/exec.rb:27:in `run' 
/app/vendor/bundle/ruby/2.2.0/gems/bundler-1.13.7/lib/bundler/cli.rb:332:in `exec' 
/app/vendor/bundle/ruby/2.2.0/gems/bundler-1.13.7/lib/bundler/vendor/thor/lib/thor/command.rb:27:in `run' 
/app/vendor/bundle/ruby/2.2.0/gems/bundler-1.13.7/lib/bundler/vendor/thor/lib/thor/invocation.rb:126:in `invoke_command' 
/app/vendor/bundle/ruby/2.2.0/gems/bundler-1.13.7/lib/bundler/vendor/thor/lib/thor.rb:359:in `dispatch' 
/app/vendor/bundle/ruby/2.2.0/gems/bundler-1.13.7/lib/bundler/cli.rb:20:in `dispatch' 
/app/vendor/bundle/ruby/2.2.0/gems/bundler-1.13.7/lib/bundler/vendor/thor/lib/thor/base.rb:440:in `start' 
/app/vendor/bundle/ruby/2.2.0/gems/bundler-1.13.7/lib/bundler/cli.rb:11:in `start' 
/app/vendor/bundle/ruby/2.2.0/gems/bundler-1.13.7/exe/bundle:34:in `block in <top (required)>' 
/app/vendor/bundle/ruby/2.2.0/gems/bundler-1.13.7/lib/bundler/friendly_errors.rb:100:in `with_friendly_errors' 
/app/vendor/bundle/ruby/2.2.0/gems/bundler-1.13.7/exe/bundle:26:in `<top (required)>' 
/app/bin/bundle:3:in `load' 
/app/bin/bundle:3:in `<main>' 
Tasks: TOP => ptourist:reset_all => ptourist:users => ptourist:delete_all => ptourist:delete_subjects 

Answer 1

このエラーが発生します。このエラーを解決する唯一の方法は、外部キーが存在するすべてのテーブルを削除するか、コンソールからそのテーブルのエントリを手動で作成することです。

たとえば、従業員表には参照として列employee_typeが含まれており、そのデータはnilです。それから、このエラーが発生する可能性があります。