Re: [sigc] Disconnection without objects [on 1.2.5]

[Martin Schulze <martin-ml hippogriff de>]

Eric, could you file a bug report at http://bugzilla.gnome.org/ ?
Just to make sure I don't forget (exam tomorrow => no time today) ...

Regards,

  Martin

Am 2003.07.29 22:24 schrieb(en) Eric Nicolas:
> Hi Martin,
>
> Thanks for your quick answer.
> This is bad news, but not too bad :-)
>
> Since my post I had a closer look to libsigc++ code, and I
> thought my proposal would be possible using a simple implementation
> of the "==" operator on slot instances. Something like:
>
>    class SignalBase {
>       Connection connect(Slot *slot)
>       {
>          impl()->push_back(slot);
>       }
>       disconnect(Slot *slot)
>       {
>          impl()->erase(slot);
>       }
>    }
>
> Where "erase()" would simply browse the existing connections and
> compare each slot remembered with the one provided using the "=="
> operator.
>
> Of course the trick would be in this operator, which would have to
> be implemented differently for each kind of slot (functor, pointer-
> to-method, ...).
>
> Anyway, this may not be feasible and was just an idea :-)
>
> ****
>
> But your proposal of clear() really does the trick for me ! It would 
> be exactly
> what I need (even though it is less "clean" than removing exactly 
> what has been
> connected).
> Could you provide this as a patch to 1.2.5 ???
>
> Thanks a lot.
>
> Eric.
>
> Martin Schulze wrote:
>
> > Hi Eric!
> >
> > Unfortunately, this is currently not supported by libsigc++.
> > Also, there is no easy way to add this feature. In the 1.2
> > series functionality would have to be added to Signal, Slot,
> > ObjectSlot, all adaptors types and some internal structures
> > which would probably mean ABI breakage.
> > In the upcoming 2.0 series it is practically impossible because
> > you can use any functor type as slot and we don't want to
> > add restrictions to this by requiring a "disconnect if you
> > hold a reference to object xy" function.
> >
> > libsigc++ doesn't really "keep track" of the objects that
> > are connected to signal. Rather, the references to your objects
> > are hidden somewhere deep in internal data structures. This
> > is the price for the great flexibility of the yet typesafe
> > library.
> >
> > However, I think it would make sense to provide a function
> > SigC::Object::clear() (or SigC::Object::clear_dependencies())
> > that would destroy _any_ connections that refer to a certain
> > object. Your example below would read:
> >
> > class Receiver : public SigC::Object {
> >   // BTW: always inherit SigC::Object for auto-disconnection
> >
> >   void connect()
> >     { emitter_.changed.connect(
> >         SigC::slot(*this, &Receiver::onChanged)); }
> >
> >   void disconnect_all()
> >     { SigC::Object::clear(); }
> > }
> >
> > Would this solve your problem? What do others think about it?
> >
> > Regards,
> >
> >   Martin
> >
> >
> > Am 2003.07.29 17:29 schrieb(en) Eric NICOLAS:
> >
> > > Hi,
> > >
> > > I'm relatively new to LibSigC++, so bear with me if this something
> > > stupid I'm asking. I've read the docs and had a look to the source
> > > code before posting here.
> > >
> > > I would like to be able to disconnect a slot without keeping a
> > > connection object. This should be possible for slots with an
> > > instance in it because the instance pointer is a unique key to
> > > the connection.
> > >
> > > If I don't have this, I have in many place in my code to keep
> > > record of the connection objects and this is really a pain and
> > > it duplicates the bookkeeping of the connections which is
> > > already well done in LibSigC++, so should not be required.
> > >
> > > So, to be more precise, I'd like this kind of behaviour:
> > >
> > > class Emitter {
> > > public:
> > >   SigC::Signal0<void> changed;
> > > };
> > >
> > > class Receiver {
> > > public:
> > >   void connect()
> > >   {
> > >     // connect the slot
> > >     emitter_.changed.connect(SigC::slot(*this, &Receiver::
> > > onChanged));
> > >   }
> > >
> > >   void disconnect()
> > >   {
> > >     // disconnect the slot
> > >     emitter_.changed.disconnect(SigC::slot(*this,
> > > &Receiver::onChanged));
> > >   }
> > > };
> > >
> > > Is this feasible with the current version of the library (1.2.5), or
> > > how
> > > difficult would it be to add this ?
> > >
> > > Thanks !
> > >
> > > _______________________________________________
> > > libsigc-list mailing list
> > > libsigc-list gnome org
> > > http://mail.gnome.org/mailman/listinfo/libsigc-list
>
>
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