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('comment')
    ques_id = request.form.get('question_id')
    author_id = User.query.filter(User.username == session.get('user')).first().id
    comm= Comment(author_id=author_id, question_id=ques_id, detail=comment)
    db.session.add(comm)
    db.session.commit()
    return redirect(url_for('detail', question_id=ques_id))

<input name="question_id" type="hidden" value="{{ ques.id }}">

<h4>评论:（{{ ques.comment|length }}）</h4>

def loginFirst(func):
    #行动前需要登录，定义装饰器
    @wraps(func)
    def wrapper(*args,**kwargs):
        if session.get('user'):
            return func(*args,**kwargs)
        else:
            return redirect(url_for('login'))
    return wrapper

<ul class="list">
            {% for foo in ques.comment %}
                <li class="post_item">
                    <a href="#" class="light">{{foo.author.username }}</a><br>
                    <p class="post_item">{{ foo.detail }}</p>
                    <span class="foot">发布于  {{ foo.create_time }}</span>
                </li>
                <hr>
            {% endfor %}
        </ul>