On 8/7/15 2:10 PM, buch...@gmail.com wrote:
Hi there,
I'm trying to do something pretty weird. I have SQLAlchemy
instrumented classes that extend a class in addition to Base, like so:
class Region(Base, t_Region):
__tablename__ = 'region'
id = Column(
mysql.INTEGER(11),
primary_key=True,
nullable=False,
autoincrement=True,
index=True,
unique=True)
name = Column(
mysql.VARCHAR(64),
nullable=False,
index=True,
default='',
unique=True)
This works great for reads because I can return it anywhere a t_Region
is expected and everything does what it is supposed to.
But now I can't figure out how to do the reverse; for example, I have
a t_Region object, and I want to insert it into the database. So far
I've got this:
mapped = Region(**region.__dict__)
This works, but it lacks elegance as it creates another object.
I'd go with that, or more likely a dedicated constructor (and I'd never
just yank __dict__ like that for schema-defined objects):
from sqlalchemy import inspect
class Region(...):
@classmethod
def as_region(cls, other):
kw = dict(
(key, getattr(other, key)) for key in
inspect(cls).attrs.keys() if hasattr(other, key)
)
return Region(**kw)
as it is the simplest. Ideally you'd not use raw t_Region objects and
instead use an appropriate factory pattern to create the Region object
up front - it's this lack of "elegance" that ultimately leads to other
elegance-lacking things like having to copy the object to the type you want.
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