refactor(soft-delete-student-class): fix issue code quality

app/controllers/course/enrol_requests_controller.rb

@@ -60,18 +60,20 @@ def create_course_user
     create_new_course_user
   end
 
-  private
-
   def restore_existing_course_user(existing_course_user)
     existing_course_user.restore
     @enrol_request.update(approve: true)
     existing_course_user
   end
 
   def create_new_course_user
-    course_user = CourseUser.new(course_user_params.reverse_merge(
-      course: current_course, user_id: @enrol_request.user_id, timeline_algorithm: current_course.default_timeline_algorithm
-    ))
+    course_user = CourseUser.new(
+      course_user_params.reverse_merge(
+        course: current_course,
+        user_id: @enrol_request.user_id,
+        timeline_algorithm: current_course.default_timeline_algorithm
+      )
+    )
 
     CourseUser.transaction do
       raise ActiveRecord::Rollback unless course_user.save && @enrol_request.update(approve: true)

app/models/course_user.rb

@@ -24,6 +24,15 @@ class CourseUser < ApplicationRecord
   # A set of roles which comprise the managers of a course.
   MANAGER_ROLES = Set[:manager, :owner].map { |v| roles[v] }.freeze
 
+  ASSOCIATED_MODELS = %i[
+    experience_points_records
+    learning_rate_records
+    course_user_achievements
+    email_unsubscriptions
+    group_users
+    personal_times
+  ].freeze
+
   validates :role, presence: true
   validates :name, length: { maximum: 255 }, presence: true
   validates :phantom, inclusion: { in: [true, false] }
@@ -179,27 +188,20 @@ def self.user?(user)
 
   # Soft delete the course user.
   def destroy
-    experience_points_records.each(&:destroy) if experience_points_records.exists?
-    learning_rate_records.each(&:destroy) if learning_rate_records.exists?
-    course_user_achievements.each(&:destroy) if course_user_achievements.exists?
-    email_unsubscriptions.each(&:destroy) if email_unsubscriptions.exists?
-    group_users.each(&:destroy) if group_users.exists?
-    personal_times.each(&:destroy) if personal_times.exists?
+    ASSOCIATED_MODELS.each do |association|
+      send(association).destroy_all
+    end
     super
   end
 
   # Restore the course user.
   def restore
     super
-    experience_points_records.with_deleted.each(&:restore) if experience_points_records.with_deleted.exists?
-    learning_rate_records.with_deleted.each(&:restore) if learning_rate_records.with_deleted.exists?
-    course_user_achievements.with_deleted.each(&:restore) if course_user_achievements.with_deleted.exists?
-    email_unsubscriptions.with_deleted.each(&:restore) if email_unsubscriptions.with_deleted.exists?
-    group_users.with_deleted.each(&:restore) if group_users.with_deleted.exists?
-    personal_times.with_deleted.each(&:restore) if personal_times.with_deleted.exists?
+    ASSOCIATED_MODELS.each do |association|
+      send(association).with_deleted.restore_all
+    end
   end
 
-
   # Test whether this course_user is a manager (i.e. manager or owner)
   #
   # @return [Boolean] True if course_user is a staff