Question

我试图在三个单独的文件中的三个模型类之间创建多对多关系：用户，项目和付款（这是关联类），但是我一直收到此错误：

sqlalchemy.exc.NoReferencedColumnError: Could not initialize target column for ForeignKey 'projects.id,' on table 'payments': table 'projects' has no column named 'id,'

尝试调试几天后，我相信我的问题是我没有元数据对象：“根据相关性对相关表进行排序，以便可以按正确的顺序创建外键约束。”在此处讨论：Understanding MetaData() from SQLAlchemy in Python

那么，如何设置元数据对象并对表进行排序，以便在各个文件中以正确的顺序创建外键约束？如果这样做，它将解决NoReferencedColumnError吗？

这是我的模型类（付款类发生错误）：

class User(UserMixin, ResourceMixin, db.Model):
    ROLE = OrderedDict([
        ('member', 'Member'),
        ('admin', 'Admin')
    ])

    __tablename__ = 'users'
    id = db.Column(db.Integer, primary_key=True)

    # Relationships.
    payments = db.relationship(
        'Project', secondary='payments', 
        backref=db.backref('payees', lazy='dynamic')
    )


class Project(ResourceMixin, db.Model):
    __tablename__ = 'projects'
    id = db.Column(db.Integer, primary_key=True)

    # Relationships.
    users = db.relationship('User', secondary="payments")#backref='users')

    fund = db.Column(db.Integer, unique=False, index=True, server_default='0')
    goal = db.Column(db.Integer, nullable=False, server_default='15000')


class Payment(ResourceMixin, db.Model):
    __tablename__ = 'payments'
    id = db.Column(db.Integer, primary_key=True)

    # Payment details.
    user_id = db.Column(db.Integer, db.ForeignKey('users.id',
                                                  onupdate='CASCADE',
                                                  ondelete='CASCADE'),
                        index=True, nullable=False)
    project_id = db.Column(db.Integer, db.ForeignKey('projects.id,'))
    amount = db.Column(db.Integer) #Error occurs on this line.

    # Relationships.
    user = db.relationship('User', backref='payments')
    project = db.relationship('Project', backref='payments')

如何在Flask-sqlalchemy中初始化元数据对象？

0 个答案: