可能很多方法,但一个是使用@validates :
from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class A(Base):
__tablename__ = 'a'
id = Column(Integer, primary_key=True)
readonly1 = Column(String)
readonly2 = Column(String)
@validates('readonly1', 'readonly2')
def _write_once(self, key, value):
existing = getattr(self, key)
if existing is not None:
raise ValueError("Field '%s' is write-once" % key)
return value
a1 = A()
a1.readonly1 = 'foo'
assert a1.readonly1 == 'foo'
try:
a1.readonly1 = 'bar'
assert False
except ValueError, e:
print e
e = create_engine("sqlite://")
Base.metadata.create_all(e)
s = Session(e)
s.add(A(readonly1='foo', readonly2='bar'))
s.commit()
a2 = s.query(A).first()
try:
a2.readonly2 = 'bar2'
assert False
except ValueError, e:
print e
@validates只是简写使用attribute events,你可以用它来打造出来的设置它的其他方式。
谢谢,我马上去看看。 – saabeilin 2013-05-16 13:39:49
属性事件url不再准确。 +1虽然 – 2016-12-09 17:11:36