Marshmallow ModelSchema to Mapping Class Inheritance SqlAlch

Question

我遇到了这个问题，我使用 ModelSchema 来验证我的 API 输入，这给了我一个数据库模型，它工作正常，但是如果我使用映射类继承(单表类型(，ModelSchema 只给我父级而没有子属性。

class SerialInterface(sql.Model):
type = sql.Column(sql.String(50))
polymorphic_identity = {
'polymorphic_identity': 'serial_interface',
'polymorphic_on': type,
}
id = sql.Column(types.Integer, primary_key=True)
transmission_rate = sql.Column(types.Integer)
mad_id = sql.Column(types.Integer, sql.ForeignKey('mad.id'))
serial_protocol = sql.relationship(SerialProtocol, uselist=False, cascade="all, delete-orphan")
class RS485(SerialInterface):
parity = sql.Column(EnumSmart(Parity))
data_bits = sql.Column(types.Integer)
stop_bits = sql.Column(types.Integer)
polymorphic_identity = SerialTypes.RS485.name
class SerialInterfaceForm(BaseSchema):
class Meta(BaseSchema.Meta):
model = SerialInterface
transmission_rate = Integer(required=True)
mad_id = Integer(required=True)
serial_protocol = Nested(SerialProtocolForm, required=True)
parity = EnumField(Parity, required=True)
data_bits = Integer(required=True)
stop_bits = Integer(required=True)

当我使用SerialInterfaceForm().load(input_json)它返回<SerialInterface (transient 1477443543280)>，使用__dict__：{'_sa_instance_state': <sqlalchemy.orm.state.InstanceState object at 0x00000157FE7F6550>, 'type': 'RS485', 'transmission_rate': 9600, 'mad_id': 1, 'serial_protocol': <SerialProtocol (transient 1477443544120)>}我的疑问是如何使棉花糖模型模式返回带有其属性的正确子项

Answer 1

我找到了解决方案，覆盖了模型模式的make_instance，并调用__mapper__.polymorphic_map找到的子类

class BaseSchema(marshmallow.ModelSchema):
@post_load
def make_instance(self, data, **kwargs):
"""Deserialize data to an instance of the model. Update an existing row
if specified in `self.instance` or loaded by primary key(s) in the data;
else create a new row.
:param data: Data to deserialize.
"""
instance = self.instance or self.get_instance(data)
if instance is not None:
for key, value in iteritems(data):
setattr(instance, key, value)
return instance
print(self.opts.model)
# kwargs, association_attrs = self._split_model_kwargs_association(data)
try:
instance = self.opts.model.__mapper__.polymorphic_map[data['type']].class_(**kwargs)
except Exception:
instance = self.opts.model(**kwargs)
for attr, value in iteritems(data):
setattr(instance, attr, value)
return instance
class Meta:
sqla_session = sql.session