<p>我同意Jonathan的一般方法,但是我觉得在会话中添加employee对象和设置employee类型应该是独立操作。下面是一个实现,它将type_name作为属性,并要求在设置会话之前将其添加到会话中:</p>
<pre><code>from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, String, Integer, ForeignKey
from sqlalchemy.orm import sessionmaker, relationship
Base = declarative_base()
Session = sessionmaker()
class EmployeeType(Base):
__tablename__ = 'employee_type'
id = Column(Integer(), primary_key=True)
name = Column(String(20))
class Employee(Base):
__tablename__ = 'employee'
id = Column(Integer(), primary_key=True)
type_id = Column(Integer(), ForeignKey(EmployeeType.id))
type = relationship(EmployeeType)
@property
def type_name(self):
if self.type is not None:
return self.type.name
return None
@type_name.setter
def type_name(self, value):
if value is None:
self.type = None
else:
session = Session.object_session(self)
if session is None:
raise Exception("Can't set Employee type by name until added to session")
self.type = session.query(EmployeeType).filter_by(name=value).one()
</code></pre>