当我使用Sendgrid Rails Heroku发送电子邮件时，如何获取或访问不同的模型属性

I am using devise, and scaffolded Textbook. I like to implement my strategy. When buyer clicks an @textbook.title -> Buyer can send an email to the @textbook's seller. I have every model has column for 'user_email' So, Whenever a seller create a @textbook, automatically current_user.email is saved into @textbook.user_email.I am using devise, and scaffolded Textbook. I l