[Python-Dev] Generic notifier module

[Fredrik Lundh]

Moshe Zadka wrote:
> > in which way is "harder to use in all common cases"
> > better?
>=20
> I'm not sure I agree this is harder to use in all common cases, but =
YMMV.
> Strings are prone to collisions, etc.

not sure what you're talking about here, so I suppose
we're talking past each other.

what I mean is that:

    model.addobserver(view.notify)
    model.removeobserver(view.notify)

works just fine without any cookies.  having to do:

    view.cookie =3D model.addobserver(view.notify)
    model.removeobserver(view.cookie)

is definitely no improvement.

and if you have an extraordinary case (like a function
pointer extracted from an object returned from a factory
function), you just have to assign the function pointer
to a local variable:

    self.callback =3D strangefunction().notify
    model.addobserver(self.callback)

    model.removeobserver(self.callback)

in this case, you would probably keep a pointer to the
object returned by the function anyway:

    self.viewer =3D getviewer()
    model.addobserver(viewer.notify)

    model.removeobserver(viewer.notify)


> And usually the code which connects
> the callback is pretty close (flow-control wise) to the code that =
would
> disconnect. FWIW, the Gtk+ signal mechanism has 3-4 different =
disconnects,
> and it might not be a bad idea, now that I think of it.

you really hate keeping things as simple as possible,
don't you? ;-)

what are these 3-4 "disconnects" doing?

> > as for the "break" functionality, I'm not sure it really
> > belongs in a basic observer class (in GOF terms, that's
>                                         ^^^ TLA overload! What's GOF?

http://www.hillside.net/patterns/DPBook/GOF.html

> > a "chain of responsibility"). but if it does, I sure prefer
> > an exception over a magic return value.
>=20
> I don't know if it belongs or not, but I do know that it is sometimes
> needed, and is very hard and ugly to simulate otherwise. That's one =
FAQ
> I don't want to answer <wink>

yeah, but the two patterns have different uses.

</F>