-Original Message-
From: sqlalchemy@googlegroups.com
[mailto:[EMAIL PROTECTED] On Behalf Of Faheem Mitha
Sent: 04 December 2008 20:43
To: sqlalchemy@googlegroups.com
Subject: [sqlalchemy] returning primary key of object without
know what it is called.
Hi,
I'm trying to figure out how to have an object return its primary key
without knowing what it is called. The docs in
http://www.sqlalchemy.org/docs/05/sqlalchemy_orm_mapper.html look
relevant, for example the function identity_key_from_instance
(see entry
from docs below), but I'm not clear about usage. The
functions on this
page look like they are meant to be used as method functions
of a mapper
object, but how should I construct such a mapper object? In my schema
file, I have lines like
Mapper(Foo, foo_table)
should I be returning an mapper object for use with
functions? Ie should I
be doing
foo_mapper = Mapper(Foo, foo_table)
or similar? The section module sqlalchemy.orm.mapper saya
This is a semi-private module; the main configurational API
of the ORM is
available in module sqlalchemy.orm.
Does this mean it is not meant to be used in this fashion?
Also, I don't understand what is meant by
This value is typically also found on the instance state under the
attribute name key.
in the docs for identity_key_from_instance below.
Please CC me on any reply.
Thanks and regards, Faheem.
You can get the mapper for a given instance using the
sqlalchemy.orm.object_mapper function, and that mapper has a
'primary_key_from_instance' method. A generic primary_key function might
look like this (untested):
import sqlalchemy.orm as orm
def get_primary_key(instance):
mapper = orm.object_mapper(instance)
return mapper.primary_key_from_instance(instance)
Hope that helps,
Simon
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