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ruby-on-rails - Rails NoMethodError（nil:NilClass 的未定义方法 `humanize'）发送至：

问题描述

我在我的 Rails 应用中有这样的工作：

class NewAnswerNotifyJob < ApplicationJob
  queue_as :default

  def perform(answer)
    Services::NewAnswerNotify.new.send_notify(answer)
  end
end

Services::NewAnswerNotify：

class Services::NewAnswerNotify
  def send_notify(answer)
    NewAnswerNotifyMailer.new.notify(answer)
  end
end

NewAnswerNotifyMailer：

class NewAnswerNotifyMailer < ApplicationMailer

  def notify(answer)
    @answer   = answer
    @question = answer.question
    @author   = answer.question.author

    mail to: @author.email
  end
end

当我尝试在 Rails 控制台中运行时（我在开发服务器上遇到了这个问题，然后在控制台中重放了这个行为）运行Services::NewAnswerNotify#send_notify时出现answer了这样的错误：

2.6.0 :023 > answer = Answer.first
  Answer Load (0.5ms)  SELECT  "answers".* FROM "answers" ORDER BY "answers"."best_solution" DESC LIMIT $1  [["LIMIT", 1]]
 => #<Answer id: 76, body: "answer body", question_id: 2, created_at: "2019-05-01 18:43:16", updated_at: "2019-05-28 15:38:16", author_id: 1, best_solution: true> 
2.6.0 :024 > Services::NewAnswerNotify.new.send_notify(answer)
  Question Load (0.6ms)  SELECT  "questions".* FROM "questions" WHERE "questions"."id" = $1 LIMIT $2  [["id", 2], ["LIMIT", 1]]
  User Load (0.4ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT $2  [["id", 1], ["LIMIT", 1]]
Traceback (most recent call last):
        3: from (irb):24
        2: from app/services/new_answer_notify.rb:3:in `send_notify'
        1: from app/mailers/new_answer_notify_mailer.rb:8:in `notify'
NoMethodError (undefined method `humanize' for nil:NilClass)
2.6.0 :025 >

因此，错误发生在mail to: @author.emailline in 中NewAnswerNotifyMailer，但是当邮件程序按计划工作时：

2.6.0 :025 > answer = Answer.first
  Answer Load (0.7ms)  SELECT  "answers".* FROM "answers" ORDER BY "answers"."best_solution" DESC LIMIT $1  [["LIMIT", 1]]
 => #<Answer id: 76, body: "for flexbox grid columns also means you can set th...", question_id: 2, created_at: "2019-05-01 18:43:16", updated_at: "2019-05-28 15:38:16", author_id: 1, best_solution: true> 
2.6.0 :026 > NewAnswerNotifyMailer.notify(answer)
  Question Load (0.5ms)  SELECT  "questions".* FROM "questions" WHERE "questions"."id" = $1 LIMIT $2  [["id", 2], ["LIMIT", 1]]
  User Load (0.3ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT $2  [["id", 1], ["LIMIT", 1]]
[i18n-debug] en.new_answer_notify_mailer.notify.subject => nil
  Rendering new_answer_notify_mailer/notify.html.slim within layouts/mailer
  Rendered new_answer_notify_mailer/notify.html.slim within layouts/mailer (4.7ms)
  Rendering new_answer_notify_mailer/notify.text.slim within layouts/mailer
  Rendered new_answer_notify_mailer/notify.text.slim within layouts/mailer (3.5ms)
NewAnswerNotifyMailer#notify: processed outbound mail in 100.5ms
 => #<Mail::Message:70164808395160, Multipart: true, Headers: <From: from@example.com>, <To: codcore@gmail.com>, <Subject: Notify>, <Mime-Version: 1.0>, <Content-Type: multipart/alternative; boundary="--==_mimepart_5d0cac2d80291_b85a3fd081039fd052340"; charset=UTF-8>>

我无法意识到问题出在哪里，为什么我会Nil在Services::NewAnswerNotify.

标签： ruby-on-railsrubyruby-on-rails-5

解决方案

几个建议：

  • 您应该直接使用 ActionMailer 类方法，而不是使用new. 这大概就是bug的来源
  • 由于您NewAnswerNotify嵌套在 下Services，因此使用根命名空间也不会那么模棱两可::NewAnswerNotifyMailer（有些人可能不同意我的观点，但我过去有很多根命名空间错误，因此我倾向于系统地使用::前缀现在）
  • 当心类加载对于class Services::NewAnswerNotify和module Services class NewAnswerNotification（关于这个主题的许多现有问题）的工作方式不同
module Services
  class NewAnswerNotify
    def send_notify(answer)
      ::NewAnswerNotifyMailer.notify(answer).deliver_now # instead of .new.notify
    end
  end
end

还有一些关于变量和英语的侧面评论

我宁愿用

  • Services::NewAnswerNotification
  • NewAnswerNotificationMailer
  • def send_notification(answer)或者def notify(answer)

从长远来看，也许是在维护代码库之后的最后一条经验建议：更明确地说明您要通知谁，def notify_question_author_of_new_answer因为稍后您可能notify_question_subscribers_of_new_answer需要通知一个或其他人（这完全取决于当然是您的商业模式，请随意忽略此评论）

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