完成注册功能

1. js文件： onclick函数return True时才提交表单，return False时不提交表单。
2. html文件：
   1. <form>中设置 action和method="post"
   2. <input> 中设置 name
3. 主py文件中：
   1. from flask import  request, redirect, url_for
   2. @app.route('/regist/', methods=['GET', 'POST’])

def regist():

   if request.method == 'GET':

        return render_template('regist.html')

   else:

        username = request.form.get(‘username’)#获取form中的数据

        判断用户名是否存在

        存到数据库中

        redirect重定向到登录页

from flask import Flask,render_template,request,redirect,url_for,session
from flask_sqlalchemy import SQLAlchemy
import config

app = Flask(__name__)
app.config.from_object(config)
db = SQLAlchemy(app)

class User(db.Model):
    __tablename__ = '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))

# user = User(username = 'misjiaojiao',password = 'misjiaojiao')
# db.session.add(user)
# db.session.commit()

# user = User.query.filter(User.username == 'misjiaojiao').first()
# db.session.delete(user)
# db.session.commit()

# user = User.query.filter(User.username == 'misjiaojiao').first()
# user.password='1234657'
# db.session.commit()

db.create_all()

@app.route('/')
def index():
    return render_template('switch切换.html')

@app.route('/login/', methods = ['GET','POST'])
def login():
    return render_template('login登录.html')

@app.route('/regist/', methods = ['GET','POST'])
def regist():
    if request.method == 'GET':
        return render_template('regist注册.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 'username existed'
        else:
            user = User(username = username,password = password,nickname = nickname)
            db.session.add(user)  # 数据库操作
            db.session.commit()
            return redirect(url_for('login'))




if __name__ == '__main__':
    app.run(debug=True)