bundle exec rails generate migration create_comments

class CreateComments < ActiveRecord::Migration
    def change
        create_table :comments do |t|
            t.string :author_name
            t.text :content
            t.integer :article_id
           t.timestamps
       end
   end

end

# app/controllers/comments_controller.rb

class CommentsController < ApplicationController

 def create
      comment = Comment.new
      comment.article_id = params[:article_id]
      comment.author_name = params[:author_name]
      comment.content = params[:content]
      comment.comment_user_id = session[:current_comment_user]['id']
      comment.save!
         
      #redirect_to :back
      redirect_to "/articles/#{params[:article_id]}"
    end   
       
  end

# app/models/comment.rb

class Comment < ActiveRecord::Base
    belongs_to :article
  end

 class Article < ActiveRecord::Base

    has_many :comments

end

 <div style='margin-top: 30px;'>
    <p>新增评论: </p>
    <%= form_tag "/comments", method: 'post' do %>
      <p>姓名:
      <%= text_field_tag "author_name" %>
      </p>
      <p>正文:
      <%= text_field_tag "content" %>
      </p>
      <input type='hidden' name='article_id' value='<%= params[:id] %>' />
      <%= submit_tag "提交" %>
    <% end %>

    <p>评论列表: </p>
    <% @comments.each do |comment| %>
      <div>
        <p>姓名: <%= comment.author_name %></p>
        <p>评论正文: <%= comment.content %></p>
      </div>
    <% end %>
  </div>