自引用关联关系 SQLalchemy [英] Self-Referential Association Relationship SQLalchemy
本文介绍了自引用关联关系 SQLalchemy的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
在我使用flask-sqlalchemy 的flask 应用程序中,我需要在两个联系人之间创建关联这是我的 Contact
模型
In my flask application with flask-sqlalchemy i need to create association between two contact
here is my Contact
model
class Contact(db.Model):
__tablename__ = 'contact'
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.Unicode(120), nullable=False, unique=False)
user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
to_contacts = db.relationship('Contact',
secondary='ContactRelation',
primaryjoin='id==contactrelation.c.from_contact_id',
secondaryjoin='id==contactrelation.c.to_contact_id',
backref='from_contacts')
和我的关联类ContactRelation
:
class ContactRelation(db.Model):
__tablename__ = 'contactrelation'
id = db.Column(db.Integer, primary_key=True)
from_contact_id = db.Column(db.Integer, db.ForeignKey('contact.id'))
to_contact_id = db.Column(db.Integer, db.ForeignKey('contact.id'))
relation_type = db.Column(db.String(100), nullable=True)
我有错误:
AttributeError: type object 'ContactRelation' has no attribute 'c'
推荐答案
感谢 Michel 和 Simon 在 SQLAlchemy 邮件列表 我需要association_proxy 和两个与Contact 关系的关系.
Thanks to Michel and Simon on SQLAlchemy mailing list i need association_proxy and two relation to Contact relation.
class Contact(db.Model):
__tablename__ = 'contact'
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.Unicode(120), nullable=False, unique=False)
created_on = db.Column(db.DateTime, default=datetime.utcnow)
birthday = db.Column(db.DateTime)
background = db.Column(db.Text)
photo = db.Column(db.Unicode(120))
user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
to_contacts = association_proxy('to_relations', 'to_contact')
from_contacts = association_proxy('from_relations', 'from_contact')
class ContactRelation(db.Model):
__tablename__ = 'contactrelation'
id = db.Column(db.Integer, primary_key=True)
from_contact_id = db.Column(db.Integer, db.ForeignKey('contact.id'))
to_contact_id = db.Column(db.Integer, db.ForeignKey('contact.id'))
relation_type = db.Column(db.String(100), nullable=True)
from_contact = db.relationship(Contact,
primaryjoin=(from_contact_id == Contact.id),
backref='to_relations')
to_contact = db.relationship(Contact,
primaryjoin=(to_contact_id == Contact.id),
backref='from_relations')
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