On Mon, Oct 4, 2010 at 5:45 PM, Michael Bayer <mike...@zzzcomputing.com> wrote: > > On Oct 4, 2010, at 8:26 PM, Ritesh Nadhani wrote: > >> Hello >> >> This has been making me pull my hair for quite sometime now :) >> >> I am trying to use MapperExtension and I have a code like: >> http://bpaste.net/show/9936/ >> >> Basically, I share the model across two apps, so I want one with the >> extension and one without. Thus the need to use one of the internal >> methods: >> >> __mapper__,exception.push(....) > >> >> Unfortunately, it the whole thing works when I use, __mapper_args__ >> but does not if I add it dynamically using the above method. Though, >> other methods like before_update, row_translate get called in both >> ways of setup. Just not reconstruct_instance, which I what I wanted. >> >> I will now startup a debugger but I was wondering if anybody knew >> about it or its a bug or its just not possible? > > It's not a bug since ad-hoc addition of extensions is not public API. The > mapper checks its extensions for this particular hook when its created and > sets an extra event listener on the class if present. > > 0.7 will allow ad-hoc listeners in a more flexible way. > > There is actually a "listener" interface for this in 0.6 which is > semi-private. It will be changing a little bit in 0.7 (whereas > MapperExtension will remain backwards compatible for at least through > 0.7/0.8). If you wanted to try that its: > > from sqlalchemy.orm.attributes import manager_of_class > > def reconstruct(instance): > print "reconstruct!" > > manager_of_class(SomeTable).events.add_listener('on_load', reconstruct) > > In this case its likely much easier to set up __mapper_args__ as a callable > on your class instead (see the examples in declarative regarding mixins - the > same technique works on the class itself), or to use the @reconstructor > decorator inside a conditional: > > class MyClass(Base): > if my_app_config_foo_bar: > �...@reconstructor > def reconstruct(self): > print "reconstruct!" > > > > > -- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To post to this group, send email to sqlalch...@googlegroups.com. > To unsubscribe from this group, send email to > sqlalchemy+unsubscr...@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/sqlalchemy?hl=en. > >
Aha. Thanks. I guess I will wait till 0.7 to use the feature. I understood the reconstructor way but not sure the mixin way. I will go now and reread the docs on the subject. -- Ritesh -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
