I found in the archives the following message: See the end of this post:
I am using sigc++-1.2 and I get a similar message to that mentioned below
whenever the parameter I am trying to bind is a reference
in the method mentioned in the "slot(...)" call.
Is this a restriction or a bug?? Does the code need to be fixed
or a note put in the documentation the the parameter that you bind
can not be a reference in the called method?
Could this be an example of the famous reference to reference problem??
I made a workaround in my code by changing the called method,
replace the referenced type T& to boost::reference_wrapper<T>.
I got reference_wrapper from the boost libraries.
The referenced_wrapper type has "value" semantics in that it
has default constructors, copy constructors and assignment operators.
What is the official libsigc+ approach to this problem?
Quoted message follows:
==================cut here with a chain saw==================
From: gtkmm mailing list account <gtkmm-list bernard-hugueney org>
To: Martin Schulze <martin-ml hippogriff de>
Cc: gtkmm-list gnome org, libsigc-list gnome org
Subject: [sigc] Re: binding by value, slot taking reference was Re: [gtkmm] binding arguments to slots
Date: Tue, 18 Nov 2003 11:23:31 +0100
Le Mardi 18 Novembre 2003 10:26, Martin Schulze a écrit :
> >
> > There is still something I don't understand with slot and bind :
> >
> > I would like to make a slot for a function taking arguments by
> > reference:
> > program :
> > "
> > using namespace std;
> > using namespace SigC;
> >
> > void foo1(int& i){++i;}
> >
> > int main(int argc, char** argv){
> > int i=1;
> > Slot0<void>slot1=bind(slot(foo1),i);
> > return 0;
> > }
>
> Try to specify the argument type as template parameter, i.e.:
>
> Slot0<void> slot1 = bind<int&>(slot(foo1), i);
I shoudl have said I already tried that :-(
>
> I'm not sure if it works, though - let us know!
same error:
/usr/include/sigc++-1.2/sigc++/bind.h: Dans static member function �
static void SigC::AdaptorBindData1_<C1>::dtor(void*) [with C1 =
int&] :
/usr/include/sigc++-1.2/sigc++/bind.h:167: instantiated from
`SigC::Slot0<R> SigC::bind(const SigC::Slot1<R, C1>&, A1) [with A1 =
int&, R = void, C1 = int&]'
testLibSigC.cxx:9: instantiated from here
/usr/include/sigc++-1.2/sigc++/bind.h:116: error: destructor name
`~int&' does not match type `int' of expression
>
> BTW in libsigc++-2.0 you will be able to write:
>
> sigc::slot<void> slot1 = sigc::bind(foo1, sigc::ref(i));
>
> instead.
Cool, I'll be missing my boost libs less :-)
(For the record, I also tried boost::ref(i) to no avail :
/usr/include/sigc++-1.2/sigc++/bind.h: Dans static member function
static void SigC::AdaptorBindData1_<C1>::dtor(void*) [with C1 =
int&] :
/usr/include/sigc++-1.2/sigc++/bind.h:167: instantiated from
`SigC::Slot0<R> SigC::bind(const SigC::Slot1<R, C1>&, A1) [with A1 =
boost::reference_wrapper<int>, R = void, C1 = int&]'
testLibSigC.cxx:11: instantiated from here
/usr/include/sigc++-1.2/sigc++/bind.h:116: error: destructor name
`~int&' does not match type `int' of expression
Now I'm really holding my breath for libsigc++-2.0 in gtkmm.
Thanks again for your kind help !
Bernard
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Paul Elliott 1(512)837-1096
pelliott io com PMB 181, 11900 Metric Blvd Suite J
http://www.io.com/~pelliott/pme/ Austin TX 78758-3117
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