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PONY ORM实体单向映射出错

ponyorm mysql python

Soutzikevich · 技术社区 · 7 年前

实体是否总是需要双向关系?

我有两张桌子。表和; 塔布莱

表

+------+----------------+-----------+
|  id  | some_attribute | tableB_id |
+------+----------------+-----------+

id =主键

some_attribute = VARCHAR

TableB_id =外键

塔布莱

+------+----------------+
|  id  | some_attribute |
+------+----------------+

身份证件 =主键

某些属性 = VARCHAR

如何使用pony orm重新创建这种关系?

我的当前代码:

# establish a connection with the database (MySQL)
db = Connection.Connection.connect_db_server_default()


class TableB(db.Entity):
    _table_ = "table_b"
    id = PrimaryKey(int, auto=False)
    some_attribute = Required(str)


class TableA(db.Entity):
    _table_ = "table_a"
    id = PrimaryKey(int, auto=False)
    some_attribute = Required(str)
    TableB_id = Set(TableA)

给出以下错误:

pony.orm.core.erdiagramerrror:表a.tableb_id的反向属性找不到

1 回复 | 直到 7 年前

Soutzikevich 7 年前

documentation

# If we want to allow an instance of OrderItem to exist without
# being assigned to an 'Order', we can define the order attribute as Optional:
class Order(db.Entity):
    items = Set(lambda: Order)

class OrderItem(db.Entity):
    order = Optional(Order)