bigdir/db/migrate/20140605025302_migrate_course_attachments.rb

class MigrateCourseAttachments < ActiveRecord::Migration
  def self.up
    # 原课程的资源数据迁移成新模式
    Attachment.all.each do |attach|
      if attach.container_type == "Project"
        project = Project.find_by_id(attach.container_id)
        if project && project.project_type == 1
          attach.container_type= 'Course'
          attach.container_id = project.course_extra.id
          attach.save
        end
      end
    end
  end

  def self.down
  end
end