课堂增加公告栏模块

db/migrate/20190830064803_add_announcement_to_course_modules.rb

@@ -0,0 +1,10 @@
+class AddAnnouncementToCourseModules < ActiveRecord::Migration[5.2]
+  def change
+    Course.all.each do |course|
+      unless course.course_modules.exists?(module_type: "announcement")
+        course.course_modules.where.not(module_type: "activity").update_all("position = position + 1")
+        course.course_modules << CourseModule.new(module_type: "announcement", hidden: 1, module_name: "公告栏", position: 2)
+      end
+    end
+  end
+end