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

   from flask import Flask,render_template,request,redirect,url_for,session
   from flask_sqlalchemy import SQLAlchemy
   import config
   from functools import wraps
   from  datetime import datetime
   
   app = Flask(__name__)
   app.config.from_object(config)
   db=SQLAlchemy(app)
   
   class User(db.Model):
       __table__name = 'user'
       id = db.Column(db.Integer,primary_key=True,autoincrement=True)
       username = db.Column(db.String(20),nullable=False)
       password = db.Column(db.String(20),nullable=False)
       nickname = db.Column(db.String(50))
   
   class Question(db.Model):
       __tablename__ = 'question'
       id = db.Column(db.Integer, primary_key=True, autoincrement=True)
       title = db.Column(db.String(100), nullable=False)
       detail = db.Column(db.Text, nullable=False)
       creat_time = db.Column(db.DateTime, default=datetime.now)
       author_id = db.Column(db.Integer, db.ForeignKey('user.id'))
       author = db.relationship('User', backref=db.backref('question'))
   
   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.Column(db.Text,nullable=False)
       question=db.relationship('Question',backref=db.backref('comments',order_by=creat_time.deac))
       author=db.relationship('User',backref=db.backref('comments'))
   
   #db.create_all()
   @app.route('/')
   def base():
       return render_template('base.html')
   
   @app.route('/index/')
   def index():
       context = {
               'question':Question.query.all()
           }
       return render_template('index.html',**context)
   
   @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)
   
   @app.route('/comment/',methods=['POST'])
   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))
   
   @app.route('/regist/',methods=['GET','POST'])
   def regist():
       if request.method=='GET':
           return render_template('regist.html')
       else:
           username=request.form.get('username')
           password=request.form.get('password')
           nickname=request.form.get('nickname')
           user=User.query.filter(User.username==username).first()
           if user:
               return u'username existed'
           else:
               user=User (username=username,password=password,nickname=nickname)
               db.session.add(user)
               db.session.commit()
               return redirect(url_for('login'))
   
   
   
   @app.route('/login/',methods=['GET','POST'])
   def login():
       if request.method=='GET':
           return render_template('login.html')
       else:
           username=request.form.get('username')
           password=request.form.get('password')
           user = User.query.filter(User.username == username).first()
           if user:
               if user.password==password:
                   session['user']=username
                   return redirect(url_for('index'))
               else:
                   return u'password error'
           else:
               return u'username is not existed'
   
   
   @app.route('/logout/')
   def logout():
       session.clear()
       return redirect(url_for('index'))
   
   
   def loginFirst(func):#定义需要登录装饰器
       @wraps(func)
       def wrapper(*args, ** kwargs):
           if session.get('user'):
               return func(*args, ** kwargs)
           else:
               return redirect(url_for('login'))
       return  wrapper
   
   
   @app.route('/question/',methods=['GET','POST'])
   @loginFirst #需要登录装饰器
   def question():
       if request.method=='GET':
           return render_template('question.html')
       else:
           title = request.form.get('title')
           detail = request.form.get('detail')
           author_id = User.query.filter(User.username == session.get('user')).first().id
           question = Question(title=title, detail=detail, author_id=author_id)
           db.session.add(question)
           db.session.commit()
           return redirect(url_for('index'))
   
   
   
   @app.context_processor
   def mycontext():
       usern=session.get('user')
       if usern:
           return{'username':usern}
       else:
           return{}
   
   
   if __name__ == '__main__':
       app.run(debug=True)

   {% extends 'base.html' %}
   
   {% block title %}问答详情{% endblock %}
   
   {% block main %}
       <div class="page-header">
               <h3>{{ ques.title }}<br><small>{{ ques.auther.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="...">
           <div class="page-gronp">
               <textarea name="new_comment"class="form-control"rows="3"id="new-comment"placeholder="write your comment"></textarea>
               <input name="question_id" type="hidden" value="{{ ques.id }}"/>
           </div>
           <button type="submit" class="btn bth-defauit">发送</button>
       </form>
   
       <h4>评论:({{ ques.comments|length }})</h4>

   <div class="" style="width:58rem;margin-left: 4%;height: auto;margin-top: 0.5% ">
       {% for foo in ques.comment %}
         <li class="list-group-item">
         <span class="glyphicon glyphicon-heart-empty"aria-hidden="true"></span>
         <a href="#" >{{ foo.author.username }}</a>
         <span class="badge">{{ foo.creat_time }}</span>
   
         <p style="...">{{ foo.detail }}</p>
         
         </li>
       {% endfor %}
   </div>

    {% endblock %}