Rails通过cookies方法来操作cookie，这和session的操作有点类似

class CommentsController < ApplicationController
  def new
    # 假如cookie中有评论者的姓名，则自动调用
    @comment = Comment.new(author: cookies[:commenter_name])
  end
 
  def create
    @comment = Comment.new(params[:comment])
    if @comment.save
      flash[:notice] = "Thanks for your comment!"
      if params[:remember_name]
        # 设置cookie
        cookies[:commenter_name] = @comment.author
      else
        # 删除cookie中的变量
        cookies.delete(:commenter_name)
      end
      redirect_to @comment.article
    else
      render action: "new"
    end
  end
end