On Monday, 25 November 2013 17:27:02 UTC+2, Michael Bayer wrote:
>
>
> On Nov 25, 2013, at 9:00 AM, George Sakkis <george...@gmail.com<javascript:>>
> wrote:
>
> > Hi all,
> >
> > is there a feature or pattern for adding a listener that is to be
> executed (at most) once? For example, say you want to send an email when
> user is created and the session is committed. If event.listen() supported a
> "once" boolean parameter, this could be expressed as:
> >
> > def email_user(email_address, message):
> > ...
> > ...
> > if valid_data:
> > new_user = User(**valid_data)
> > db.session.add(new_user)
> > # send an email to new_user after committing
> > event.listen(db.session, "after_commit",
> > once=True, # hypothetical parameter
> > lambda session: email_user(new_user.email,
> "welcome
> {}!".format(new_user.name<http://www.google.com/url?q=http%3A%2F%2Fnew_user.name&sa=D&sntz=1&usg=AFQjCNHUYRuAKfHoBRBgPDAOZm4sTiKzOg>))
>
>
>
> there are certain events such as pool.first_connect that use a “once” type
> of system, but that is linked to the type of event.
>
> I haven’t tried this but you should be able to call event.remove()
> (sqlalchemy 0.9) within the handler:
>
> def go(session):
> email_user(…)
> event.remove(session, “after_commit”, go)
> event.listen(session, “after_commit”, go)
>
Nice, this should do the trick, thanks. Any workaround for 0.7.x-0.8.x ?
George
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