> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Daniel Robbins
> Sent: 22 March 2010 20:45
> To: [email protected]
> Subject: Re: [sqlalchemy] recommended declarative method
> design pattern for sessions
>
> On Mar 22, 2010, at 5:10 AM, King Simon-NFHD78 wrote:
>
>
> See the 'How can I get the Session for a certain
> object' question at
>
> http://www.sqlalchemy.org/docs/session.html#frequently-asked-questions
>
> Basically, in your FindFriends method, replace:
>
> session = Session()
>
> with:
>
> session = Session.object_session(self)
>
>
>
> The reference documentation seems to indicate that
> Session.object_session() will return the existing session if
> one exists, rather than providing a new session that must be
> separately closed.
>
> Is this correct? If so, then FindFriends() should not close
> the session acquired via Session.object_session(obj), correct?
>
> Is it possible for object_session() to return None if the
> object's session was previously close()d?
>
> Thanks,
>
> Daniel
>
object_session does indeed return the session that the instance is
already bound to (so you shouldn't close it). I didn't know what
object_session would return if the original session had been closed, so
I tried it:
import sqlalchemy as sa
import sqlalchemy.orm as saorm
import sqlalchemy.ext.declarative as decl
Base = decl.declarative_base()
class User(Base):
__tablename__ = 'user'
id = sa.Column(sa.Integer, primary_key=True)
name = sa.Column(sa.String)
engine = sa.create_engine('sqlite://')
Base.metadata.create_all(bind=engine)
Session = saorm.sessionmaker(bind=engine)
sess = Session()
print "Original session is", sess
u1 = User(name='Daniel')
sess.add(u1)
sess.commit()
print "Before closing session, object_session returns",
print Session.object_session(u1)
sess.close()
print "After closing session, object_session returns",
print Session.object_session(u1)
Which produced the following output:
Original session is <sqlalchemy.orm.session.Session object at
0xb705a36c>
Before closing session, object_session returns
<sqlalchemy.orm.session.Session object at 0xb705a36c>
After closing session, object_session returns None
So I guess object_session already does what you want.
Hope that helps,
Simon
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