Hi all,
I'd like to have an Entity able to be "attached" to N different others,
avoiding the need of N intermediate/secondary tables.
I imagine something like the following::
class Address(Base):
__tablename__ = 'addresses'
id = Column(Integer, primary_key=True)
attached_kind = Column(String)
attached_to = Column(Integer)
street = Column(String)
city = Column(String)
state = Column(String)
zip = Column(String)
class Person(Base):
__tablename__ = 'persons'
id = Column(Integer, primary_key=True)
name = Column(String)
addresses = relationship(
Address,
uselist=True,
primaryjoin="and_(Address.attached_to==Person.id,
Address.attached_kind='Person')")
class Home(Base):
__tablename__ = 'homes'
id = Column(Integer, primary_key=True)
name = Column(String)
addresses = relationship(
Address,
uselist=True,
primaryjoin="and_(Address.attached_to==Home.id,
Address.attached_kind='Home')")
This is really a variant of
http://docs.sqlalchemy.org/en/rel_1_1/orm/join_conditions.html#specifying-alternate-join-conditions
except that the Address entity carries a tuple of (remote_object_kind,
remote_object_id) that uniquely identify the related object.
The above partially works, but as explained in the doc, SA does not populate
the "attached_*" fields when I do something like::
newaddr = Address(street='somewhere')
person.addresses.append(newaddr)
so I have to do this instead::
newaddr = Address(street='somewhere', attached_kind='Person',
attached_id=person.id)
Is there any trick hidden somewhere, or do I need a add_address() method on
each entity?
Thank you for any hint,
ciao, lele.
--
nickname: Lele Gaifax | Quando vivrò di quello che ho pensato ieri
real: Emanuele Gaifas | comincerò ad aver paura di chi mi copia.
[email protected] | -- Fortunato Depero, 1929.
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