未初始化的常量 SubscribersController

看起来我在我的代码中已经清楚地说明了一切，但我总是收到未初始化的常量错误。在我的 routes.rb 我有：

Rails.application.routes.draw do
  get 'welcome/index'

  resources :articles do
    resources :comments
    collection do
      get :search #creates a new path for searching
    end
  end
  resources :subscribers
  root 'welcome#index'

end

在我的控制器 subcribers_controller.rb 文件中，我有：

class SubscribersController < ApplicationController
  def index
  end

  def create
    @subscriber = Subscriber.new(subscriber_params)
#check if email exists in database
      if Subscriber.exists?(email: @subscriber.email)
        redirect_to root_path, alert:
        "Sorry, that email already exists!"
      elsif @subscriber.save
        redirect_to root_path, notice:
        "Thank you #{@subscriber.f_name}, for subscribing to my Newslatter!"
      else
        redirect_to root_path, alert:
        "Sorry, I failed to save your information. Please, try again!"
      end
  end

  private

    def subscriber_params
      params.require(:subscriber).permit(:f_name, :l_name, :email, :country)
    end
end

在视图文件中：

  <%= form_for :subscriber, url: subscribers_path do |f| %>
      <%= f.text_field :f_name, placeholder: "First Name",
                         class:"form-control mr-sm-2" %>
      <%= f.text_field :l_name, placeholder: "Last Name",
                         class:"form-control mr-sm-2" %>
      <%= f.email_field :email, placeholder: "Your Email",
                         class:"form-control mr-sm-2" %>
      <%= f.select :country,
            options_for_select(['Country1', 'County2', 'County3', 'County4']),
            prompt: 'Select your Country' %>
      <%= f.submit 'Submit', class:"btn btn-light my-2 my-sm-0" %>
      <% end %>

我卡住了，不知道如何解决。我阅读了有关该问题的类似主题，但没有帮助。