简单要实现的功能是：如果用户提交了一个表单，触发保存方法后就执行发送邮件通知。

controller代码：

if @work.save
        Usermailer.workcreated_email(@work).deliver_now
        format.html {redirect_to @work, notice: "Work Created"}
        format.js {}
      else
        format.html {render 'new'}
        format.js {}
      end

usermailer.rb:

class Usermailer < ApplicationMailer
  default from: "chaniel_test@163.com"

  def workcreated_email(work)
    @work = work
    mail(to: work.project.user.email, subject: "Work Item Posted")
  end
end

console 报错：

Usermailer#workcreated_email: processed outbound mail in 31.5ms
Completed 500 Internal Server Error in 127ms (ActiveRecord: 3.1ms)

ActionView::MissingTemplate (Missing template usermailer/workcreated_email with "mailer". Searched in:
  * "usermailer"
):
  app/mailers/usermailer.rb:6:in `workcreated_email'
  app/controllers/works_controller.rb:21:in `block in create'
  app/controllers/works_controller.rb:19:in `create'