从首页问答标题到问答详情页

主PY文件写视图函数，带id参数。 

@app.route('/detail/<question_id>')
def detail(question_id):
    quest = 
    return render_template('detail.html', ques = quest)

@app.route('/detail/<question_id>')
def detail(question_id):
    quest = Question.query.filter(Question.id == question_id).first()
    return render_template('detail.html',ques =quest)

首页标题的标签做带参数的链接。
      {{ url_for('detail',question_id = foo.id) }}

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

{% block main %}
    <p>{{ username }}用户,welcome</p>
<h1></h1>
<h2>欢迎光临</h2>
    <ul class="list-group">
        {% for foo in questions %}
            <li style="box-shadow: #cccccc" class="list-group-item">
                <span class="glyphicon glyphicon-leaf" aria-hidden="true"></span>
                <a href="">{{foo.author.username}})</a>
                <br>
                <a href="{{ url_for('detail',question_id=foo.id) }}" class="title">{{foo.title}}</a>
                <br>
                <span class="badge">{{foo.creat_time}}</span>
                <p class="detail">{{foo.detail}}</p>
             </li>
        {% endfor %}
    </ul>
{% endblock %}
<!--评论:({{foo.comments.length }}-->
<!--<a href="{{url_for('usercenter',user_id = foo.author_id)}}">{{foo.author.username}}评论:({{foo.comments.length }})</a>-->

在详情页将数据的显示在恰当的位置。 

{{ ques.title}}
{{ ques.id  }}{{  ques.creat_time }}

{{ ques.author.username }} 
{{ ques.detail }}

{% extends'base.html' %}
{% block title %}
    问答详情
{% endblock %}
{% block head %}
     <!-- 引入 Bootstrap -->
    <link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet">
{% endblock %}
{% block main %}

<h3 >问题详情</h3>
<div class="container">
    <div class="row clearfix">
        <div class="col-md-12 column">
            <h3 class="text-center">
                {{ques.title}}<br>
                <small>{{ques.author.username}}
                </small>
                <span>{{ques.creat_time}}</span>
            </h3>

            <p class="text-center">
                 {{ques.detail}}
            </p>
            <form role="form">
                <div class="form-group">
                     <label for="exampleInputEmail1">Write down your comment</label>
                    <input type="email" class="form-control" id="exampleInputEmail1" />
                </div>
                 <button type="submit" class="btn btn-default">提交</button>
                <br>
            </form>
        </div>
    </div>
</div>
{% endblock %}

<!--{{ques.title}} {{ques.author.username}} {{ques.creat_time}} {{ques.detail}}-->
<!--pinglun:({{ques.comment[length}})-->

建立评论的对象关系映射：

class Comment(db.Model):
    __tablename__='comment'

class Comment(db.Model):
    __tablename__='comment'
    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    author_id = db.Column(db.Integer, db.ForeignKey('user.id'))
    question_id = db.Column(db.Integer , db.ForeignKey('question.id'))
    creat_time = db.Column(db.DateTime,default=datetime.now)
    detail = db.Colunmn(db.Text , nullable=False)
    question = db.relationship('Question',backref = db.backref('comments'))
    author = db.relationship('User',backref = db.backref('comments'))