完成评论功能

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

@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('xiangqing',question_id=ques_id))

{% extends 'base.html' %}
{%  block title %}问答详情{% endblock %}
{% block main %}
<div class="page-header">
    <h3>{{ ques.title }}<br><small>{{ ques.author.username }} <span class="badge">{{ ques.creat_time }}</span> </small></h3>

</div>
<p class="lead">{{ ques.detail }}</p>
<hr>
<form action="{{ url_for('comment') }}" method="post" style="..."...></form>
    <div class="form-group">
    <textarea name ="new_comment" class="form-control" rows="3"id="new-comment" placeholder="write your comment"></textarea>
    </div>
    <botton type="submit" class="btn btn-default">发送</botton>
<h4>评论:({{ ques.comments|length }}</h4>

<ul class="list-group" style=""></ul>
{%  endblock %}

{% extends 'detail.html' %}
{% block title %}首页{% endblock %}

{% block main %}
    <img sr="{{ url_for('staic',filename='images/qalogo.png') }}" alt="qa">
    <ul class="list-group" style="....">
    {% for foo in question %}
        <li class="list-group-items">
        <span class="glyphicon glyphicon-leaf" aria-hidden="="true></span>
        <a href="{{ url_for('detail',question_id =foo.id) }}">{{ foo.title }}</a>
        <p style="">{{ foo.detail }}</p>
        <span class="glyphicon glyphicon-user" aria-hidden="true"></span>
        <a href="{{ url_for('usercenter',user_id=foo.author_id) }}">{{ foo.author.username }}评论:({{ foo.comments|length }})</a>
        <span class="badge">{{ foo.creat_time }}</span>

        </li>
    {% endfor %}

    </ul>

{% endblock %}