如何使notifiers文件夹的文件特定于模型？
app文件夹下的所有代码都是在没有任何配置的情况下加载的。您只需要遵守类的命名约定。在这种情况下 UserNotifier 这个名字对吗 app/notifiers/user_notifier.rb .
该文件user_notifier.rb方法如何可用于用户模型？

# app/models/application_record.rb

class ApplicationRecord < ActiveRecord::Base
  # your code

  def send_notification(notification_name, recipients)
    notifier = "#{self.class.name}Notifier".constantize.new()
    send(notification_name, recipients)
  end
end

# app/models/user.rb

class User < ApplicationRecord
  # your code

  # a method where you want to send a notification
  def foo
    send_notification(:reminder, [id])
  end
end

# app/notifiers/user_notifier.rb

class UserNotifier < ApplicationNotifier
  def reminder(recipients)
   {
     type: 'sms',
     content: 'hi everyone',
     recipients: recipients
   }
  end
end

多亏了léonard，他发布了解决方案，但在编写gem时，我们需要从gem处理这些配置。因为当有人使用我们的gem时，他/她不必手动在application_record.rb中编写任何与配置相关的逻辑。
发布它只是为了确保将来它可能对其他人有所帮助。
我是如何解决这个问题的（为了将gem附加到一个模型中，我们在希望配置它的模型中添加了act_as_notifier）
在通知程序gem的model_config.rb类中
拥有@model_类并查找相应的通知程序类
在通知程序类中添加attr_访问器，并用model对象初始化它
还定义自定义getter和setters通知程序属性

# rails_notifier/model_config.rb

    def initialize(model_class)
      @model_class = model_class

      # get model corresponding notifier class
      # for User model class, there would UserNotifier class
      # under notifiers folder of app directory
      # getting notitifer class name
      notifier_class = "#{@model_class.name}Notifier"

      # Notifier class attribute set later set with model object
      attribute_name = @model_class.name.underscore

      # register a `notifier` method in model class
      # 'method_name' is a method of notifier class
      # and options hash contain sender
      @model_class.class_eval do
        define_method(:notifier) do |method_name, options|
          # create notifier class object
          notifier_ = notifier_class.constantize.new

          # define setter for notifier attribute
          notifier_.send(:define_singleton_method, "#{attribute_name}=".to_sym) do |value|
            instance_variable_set("@" + attribute_name.to_s, value)
          end

          # define getter for notifier attribute
          notifier_.send(:define_singleton_method, attribute_name.to_sym) do
            instance_variable_get("@" + attribute_name.to_s)
          end

          # self point to the object of model
          # e.g User.last.notifier(:send_reminder), slef = User.last
          # set notifier attribute with model object
          notifier_.send("#{attribute_name}=".to_sym, self)
          notifier_hash = notifier_.send(method_name)
          RailsNotifier.notify(notifier_hash) if notifier_hash.present?
        end
      end
    end