Rails NoMethodError (undefined 方法 'humanize' for nil：NilClass) 在邮件中发送至：

Question

我的 Rails 应用程序中有这样的工作：

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(我在开发服务器上遇到此问题，然后在控制台中重播此行为)以answer运行Services::NewAnswerNotify#send_notify时，我收到以下错误：

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NewAnswerNotifyMailermail to: @author.email行中，但是当邮件程序本身按计划工作时：

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: [e-mail]>, <To: [e-mail]>, <Subject: Notify>, <Mime-Version: 1.0>, <Content-Type: multipart/alternative; boundary="--==_mimepart_5d0cac2d80291_b85a3fd081039fd052340"; charset=UTF-8>> 

我不知道问题出在哪里，为什么我在Services::NewAnswerNotifyNil.

Answer 1

几个建议：

• 您应该直接使用 ActionMailer 类方法，而不是使用new实例化新的邮件程序。这可能是错误的根源
• 由于您的NewAnswerNotify嵌套在Services下，因此使用根命名空间::NewAnswerNotifyMailer也会减少歧义(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，我现在倾向于系统地使用::前缀)
• 当心类加载对class Services::NewAnswerNotify和module Services class NewAnswerNotification的工作方式不同(关于此主题的许多现有问题)

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

我宁愿使用

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

从长远来看，也许从维护代码库后的经验中得出的最后一条建议：更明确地说明您通知谁def notify_question_author_of_new_answer，因为稍后您可能会有notify_question_subscribers_of_new_answer或其他人可能需要通知(当然，这完全取决于您的商业模式， 随意忽略此评论)