flask sqlchemy 多对多的自引用关系定义

时间:2021-06-10 17:35:20

多对多的定义可以使用关联表,或者重新定义一个模型,通过模型定义多对多的自引用在flask web开发书里有讲到,这里主要演示用关联表定义的方法。

from flask_sqlalchemy import SQLAlchemy
from flask import Flask app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////tmp/test.db'
db = SQLAlchemy(app)
follows=db.Table('follows',
db.Column('follower_id',db.Integer,db.ForeignKey('users.id')),
db.Column('followed_id',db.Integer,db.ForeignKey('users.id')))
class User(db.Model):
__tablename__ = 'users'
id = db.Column(db.Integer, primary_key=True)
username = db.Column(db.String(64), unique=True, index=True) followers=db.relationship('User',
secondary=follows,
primaryjoin=id==follows.c.followed_id,
secondaryjoin=id==follows.c.follower_id,
backref=db.backref('followed',lazy='dynamic'),
lazy='dynamic')
u1,u2=User(username='u1'),User(username='u2')
u1.followed.append(u2)
print "u1 following :",u1.followed[0].username
print "u2 followers :",u2.followers[0].username

表中定义了关注的人,和粉丝两个字段。主要需要设置primaryjoin跟secondaryjoin参数