如何在没有设计的情况下设置act_as_votable？

我正在关注这篇文章（我试图让人们在不登录的情况下进行投票，每次投票1 ip），当我按下upvote按钮时，出现以下错误：

评论控制器中的NoMethodError #upvote＃的未定义方法`find_or_create_by_ip'

提取的源（第7行附近）：

5      @comment = Comment.find(params[:id])
6      session[:voting_id] = request.remote_ip
7      voter = Session.find_or_create_by_ip(session[:voting_id])
8      voter.likes @comment
9      flash[:message] = 'Thanks for voting!'
10     respond_to do |format|

我遵循了帖子中的所有内容，创建了一个Session模型并将所有代码添加到我的文件中。这是我的代码：

#routes.rb

Rails.application.routes.draw do
  resources :posts  do
    resources :comments do
      member do
        post :upvote
      end
    end
  end

  root "posts#index"
end

#models:

class Post < ActiveRecord::Base
    has_many :comments
end

class Comment < ActiveRecord::Base
  belongs_to :post
  acts_as_votable
end

class Session < ActiveRecord::Base
    acts_as_voter
end

#controller:
class CommentsController < ApplicationController
  before_action :set_post

  def upvote
    @comment = Comment.find(params[:id])
    session[:voting_id] = request.remote_ip
    voter = Session.find_or_create_by_ip(session[:voting_id])
    voter.likes @comment
    flash[:message] = 'Thanks for voting!'
    respond_to do |format|
      format.html { redirect_to :back }
      format.js
    end
  end

  def create
    @comment = @post.comments.create(comment_params)
    redirect_to root_path
  end

  def destroy
    @comment = @post.comments.find(params[:id])
    if @comment.destroy
      flash[:success] = "Comment was deleted."
    else
      flash[:error] = "Comment could not be deleted."
    end
    redirect_to root_path
  end

  private

  def set_post
    @post = Post.find(params[:post_id])
  end

  def comment_params
    params[:comment].permit(:content)
  end
end