On 11/05/2016 08:45 PM, Yegor Roganov wrote:
Thank, I haven't yet figured out how to make your code more general
(without having to specify 'user_id'), but I think it can be done.
In the meantime I came up with a somewhat gross solution of my own.
The idea is to declare relation as `viewonly=True` and to delegate sets
to an injected write-only relationship (injection is the gross part).
I'm curious to hear your opinion on this approach, if possible.
it looks like recipes I wrote before we had decent events in place, it's
fine.
Here is the code:
|
from sqlalchemy import Column, Integer, String, ForeignKey, Boolean
from sqlalchemy import create_engine, and_
from sqlalchemy import event
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relationship, mapper
from sqlalchemy.orm import sessionmaker
Base = declarative_base()
engine = create_engine('sqlite:///:memory:', echo=False)
Session = sessionmaker(bind=engine)
def soft_deleting_relationship(target, primaryjoin):
assert issubclass(target, Base)
rel = relationship(target,
primaryjoin=primaryjoin,
viewonly=True,
uselist=False,
)
@event.listens_for(mapper, 'after_configured', once=True)
def configure():
key = '_all_child_' + rel.key
parent = rel.parent.class_
if not hasattr(parent, key):
setattr(parent, key, relationship(target, lazy="noload"))
@event.listens_for(rel, 'set', active_history=True)
def set(target, value, oldvalue, initiator):
if oldvalue is not None:
oldvalue.delete()
getattr(target, key).append(value)
return rel
class User(Base):
__tablename__ = 'users'
id = Column(Integer, primary_key=True)
class Address(Base):
__tablename__ = 'addresses'
id = Column(Integer, primary_key=True)
email = Column(String, nullable=False)
deleted = Column(Boolean, nullable=False, default=False)
user_id = Column('user_id', Integer, ForeignKey('users.id'))
def delete(self):
self.deleted = True
User.address = soft_deleting_relationship(
Address,
primaryjoin=lambda: and_(Address.user_id == User.id,
~Address.deleted),
)
def test():
Base.metadata.create_all(engine)
sess = Session()
a1 = Address(email='foo')
u = User(id=1, address=a1)
sess.add_all([u, a1])
sess.commit()
a2 = Address(email='bar')
u.address = a2
sess.commit()
assert a1.user_id == 1, a1.user_id
assert u.address.id == a2.id
assert a2.id is not None
assert a1.deleted
test()
|
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http://www.sqlalchemy.org/
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SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
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