コントローラーでしていた処理をモデルで処理する

app/controllers/api/notifications/unread_controller.rb

@@ -4,15 +4,15 @@ class API::Notifications::UnreadController < API::BaseController
   def index
     checked_unread_notifications = current_user.notifications.checked_unreads
     checked_unread_notifications.each do |notification|
-      notification_path = notification[:path]
-      model = notification_path.split('/')[1].classify.constantize
-      id = notification_path.split('/')[2]
+      notification_path = notification.notified_path
+      model = notification.notified_model
+      id = notification.notified_id
       comments = model.find(id).comments
-      if comments.pluck(:user_id).include?(notification.sender.id)
-        latest_notification = current_user.notifications.unreads.where(path: notification_path)[0]
-        new_message = notification.message.gsub(/を確認しました。/, 'の確認とコメントをしました。')
-        notification.update(message: new_message, kind: 'check_and_comment', created_at: latest_notification.created_at + 3)
-      end
+      next unless comments.pluck(:user_id).include?(notification.sender.id)
+
+      latest_notification = current_user.notifications.unreads.where(path: notification_path).maximum(:created_at)
+      new_message = notification.message.gsub(/を確認しました。/, 'の確認とコメントをしました。')
+      notification.update(message: new_message, kind: 'check_and_comment', created_at: latest_notification + 3)
     end
     @notifications = if params[:page]
                        current_user.notifications

app/models/notification.rb

@@ -196,4 +196,16 @@ def self.following_report(report, receiver)
   def self.into_one
     select(:path).group(:path).maximum(:created_at)
   end
+
+  def notified_path
+    self[:path]
+  end
+
+  def notified_model
+    notified_path.split('/')[1].classify.constantize
+  end
+
+  def notified_id
+    notified_path.split('/')[2]
+  end
 end