完成评论功能

1. 定义评论的视图函数
   @app.route('/comment/',methods=['POST'])
   def comment()：

   @app.route('/comment/',methods=['POST'])
   @loginFirst
   def comment():
       comment=request.form.get('new_comment')
       ques_id=request.form.get('question_id')
       auth_id=User.query.filter(User.username==session.get('user')).first().id
       comm=Comment(author_id=auth_id,question_id=ques_id,detail=comment)
       db.session.add(comm)
       db.session.commit()
       return redirect(url_for('detail',question_id=ques_id)

   
   读取前端页面数据，保存到数据库中
2. 用<input type="hidden" 方法获取前端的"question_id" 

   <div class="new-comment">
           <textarea name="new_comment" id="new-comment" cols="85" rows="5" placeholder="评论..."></textarea>
           <input name="question_id" type="hidden" value="{{ ques.id }}">
       </div>
   

   　　

3. 显示评论次数

   <h4 style="color:#5b5b5b;">{{ ques.comments|length }}条评论</h4>
   

   　　

4. 要求评论前登录
5. 尝试实现详情页面下的评论列表显示

   <ul class="list">
          {% for foo in ques.comments %}
          <li class="post_item">
              <a href="#" class="light">{{foo.author.username }}</a>
              <br>
              <img width="48" height="48" class="pf" src="https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=4066191998,32277144&fm=27&gp=0.jpg" alt="">
              <p class="post_item">{{ foo.detail }}</p>
              <span class="foot">发布于  {{ foo.create_time }}</span>
          </li>
          <hr>
   {% endfor %}
      </ul>