flask_sqlalchemy python3.9+ 的关系

Question

我找不到通过 user.messages 和通过 channel.messages[ 获取用户所有消息的方法=27=]。我一直收到外键错误。我需要改变我的人际关系什么才能让它发挥作用？

我希望能够： user.messages 和 channel.messages

作为额外的（如果可能的话）： message.user.username 或 message.user.id

我的类:

class User(db.Model, UserMixin): id = db.Column(db.Integer, primary_key=True) username = db.Column(db.String(20), unique=True, nullable=False) password = db.Column(db.String, nullable=False) email = db.Column(db.String, unique=True, nullable=False) admin = db.Column(db.Boolean, default=False) mc_access = db.Column(db.Boolean, default=False) pass_recov_code = db.Column(db.String, default=None) all_messages = db.relationship("Message", backref=db.backref("Message"), primaryjoin="foreign(User.id) == remote(Message.sender_id)", foreign_keys="[User.id, User.username]", cascade="all, delete" ) class Channel(db.Model): id = db.Column(db.Integer, primary_key=True) name = db.Column(db.String(20), unique=True, nullable=False) uses_password = db.Column(db.Boolean, default=False) password = db.Column(db.String) online_users = db.Column(db.String, default=json.dumps([])) messages = db.relationship("Message", cascade="all, delete", foreign_keys="[Channel.id]", backref=db.backref("channel")) maker_id = db.Column(db.Integer, nullable=False) class Message(db.Model): id = db.Column(db.Integer, primary_key=True) sender_id = db.Column(db.Integer, db.ForeignKey("user.id"), nullable=False) sender_username = db.Column(db.String, db.ForeignKey("user.username"), nullable=False) channel_id = db.Column(db.Integer, db.ForeignKey("channel.id"), nullable=False) message = db.Column(db.String, default="", nullable=False) send_on = db.Column(db.String, nullable=False) edited = db.Column(db.Boolean, default=False)

Answer 1

只需执行以下操作：

class User(db.Model, UserMixin):

    ...

    messages = db.relationship("Message", back_populates="user")


class Channel(db.Model):
    
    ...

    messages = db.relationship("Message", back_populates="channel")


class Message(db.Model):
    
    ...
    
    sender_id = db.Column(db.Integer, db.ForeignKey("user.id"), nullable=False)
    channel_id = db.Column(db.Integer, db.ForeignKey("channel.id"), nullable=False)

    user = db.relationship("User", back_populates="messages")
    channel = db.relationship("Channel", back_populates="messages")

这样就可以使用user.messages,channel.messages,message.user.username 和 message.user.id.

注意：你也可以使用backref代替back_populates，但我建议使用back_populates，因为它更明确。

flask_sqlalchemy python3.9+ 的关系

relationship for flask_sqlalchemy python3.9+

python

sqlalchemy

flask-sqlalchemy