Question

我有3个使用Flask-SQLalchemy创建的模型：User，Role，UserRole

user.py：

class Role( ActiveRecord, db.Model ):

    __tablename__ = "roles"

    #   Schema
    id = db.Column( db.Integer, primary_key = True )
    name = db.Column( db.String( 24 ), unique = True )
    description = db.Column( db.String( 90 ) )

    users = db.relationship( "User", secondary = "UserRole", \
        backref = db.backref( "roles" ) )

role.py：

class User( db.Model, ActiveRecord ):

    __tablename__ = "users"

    #   Schema
    id = db.Column( db.Integer, primary_key = True )
    email = db.Column( db.String( 90 ), unique = True )
    password = db.Column( db.String( 64 ) )

    #   Relations
    roles = db.relationship( "Role", secondary = "UserRole", \
        backref = db.backref( "users" ) )

user_role.py：

class UserRole( ActiveRecord, db.Model ):

    __tablename__ = "user_roles"

    #   Schema
    user_id = db.Column( db.Integer, db.ForeignKey( 'users.id' ), primary_key = True )
    role_id = db.Column( db.Integer, db.ForeignKey( 'roles.id' ), primary_key = True )

如果我尝试（在控制台中）通过User.query.all()让所有用户获得AttributeError: 'NoneType' object has no attribute 'all'，如果我再试一次，我会收到另一个错误：

sqlalchemy.exc.InvalidRequestError: One or more mappers failed to initialize - can't proceed with initialization of other mappers.  Original exception was: type object 'UserRole' has no attribute 'foreign_keys'

任何人都可以了解我做错了什么吗？我想几个月前我的代码运行正常，但我最近更新了SQLAlchemy，Flask和Flask-SQLAlchemy，它停了下来。这只是一个辅助项目。

Answer 1

这里有点难，因为你正在使用一些未知的基类，如“ActiveRecord”等。但是，它看起来非常像“次要”参数是错误的：

class User( db.Model, ActiveRecord ):

    __tablename__ = "users"

    #   Schema
    id = db.Column( db.Integer, primary_key = True )
    email = db.Column( db.String( 90 ), unique = True )
    password = db.Column( db.String( 64 ) )

    #   Relations
    roles = db.relationship( "Role", secondary = "UserRole", \
        backref = db.backref( "users" ) )

secondary需要引用Table对象，而不是映射类，如果按字符串名称，那么它将是"user_roles"：

    roles = db.relationship( "Role", secondary = "user_roles", \
        backref = db.backref( "users" ) )

Flask-SQLAlchemy - 模型没有属性'foreign_keys'

1 个答案: