Rails routes.rbに書く順番

routes.rbとルーティング

routes.rb

Rails.application.routes.draw do
  resources :records

  root 'records#index'
end

例えば上のようにrecordsモデルに対してルーティングを設定した場合、rails routesの実行すると以下

                   Prefix Verb   URI Pattern                      Controller#Action
                  records GET    /records(.:format)               records#index
                          POST   /records(.:format)               records#create
               new_record GET    /records/new(.:format)           records#new
              edit_record GET    /records/:id/edit(.:format)      records#edit
                   record GET    /records/:id(.:format)           records#show
                          PATCH  /records/:id(.:format)           records#update
                          PUT    /records/:id(.:format)           records#update
                          DELETE /records/:id(.:format)           records#destroy
                     root GET    /                                records#index

ページを追加する

新しいHTMLページを追加しようとしてroutes.rbを編集した

routes.rb

Rails.application.routes.draw do
  resources :records
  get "records/all" => "records#all"

  root 'records#index'
end

ルーティングテーブルの下から二行目に追加された

                   Prefix Verb   URI Pattern                      Controller#Action
                  records GET    /records(.:format)               records#index
                          POST   /records(.:format)               records#create
               new_record GET    /records/new(.:format)           records#new
              edit_record GET    /records/:id/edit(.:format)      records#edit
                   record GET    /records/:id(.:format)           records#show
                          PATCH  /records/:id(.:format)           records#update
                          PUT    /records/:id(.:format)           records#update
                          DELETE /records/:id(.:format)           records#destroy
             records_all  GET    /records/all(.:format)           records#all
                     root GET    /                                records#index

しかしこの状態で/records/allにアクセスすると「コントローラにshowメソッドが存在しません」のエラー
showメソッドなんて呼んでないのに・・・

解決策

routes.rb

Rails.application.routes.draw do
  get "records/all" => "records#all"
  resources :records

  root 'records#index'
end

すごく単純にroutes.rbでの順番を入れ替えるだけ

                   Prefix Verb   URI Pattern                      Controller#Action
             records_all  GET    /records/all(.:format)           records#all
                  records GET    /records(.:format)               records#index
                          POST   /records(.:format)               records#create
               new_record GET    /records/new(.:format)           records#new
              edit_record GET    /records/:id/edit(.:format)      records#edit
                   record GET    /records/:id(.:format)           records#show
                          PATCH  /records/:id(.:format)           records#update
                          PUT    /records/:id(.:format)           records#update
                          DELETE /records/:id(.:format)           records#destroy
                     root GET    /                                records#index

もともとルーティングテーブルは上から読んでいくので、/records/allの設定が/records/:idより後ろにあると先に/records/:idに引っかかり、showメソッドを呼び出そうとしてしまう