Re: [sigc] is it possible to disconnect without storing `sigc::connection'?

[klaus triendl <triendl kj aon at>]

Paul Davis schrieb:
> On Wed, 2006-10-11 at 21:19 +0300, Paul Pogonyshev wrote:
>> Right, I know this.  I wondered if I could not store connection objects,
>> as I know what handlers _this_ object has connected to a signal.  I wished
>> to remove them just by (object + function) pair.
>>
>> Here is situation I have.   Object A has a pointer to some model, B.  It
>> connects to some signals in B to listen for some events.  Now, if the
>> model changes to C, A has to disconnect its handlers from B and connect
>> them to C instead.  I wondered if I could do that without storing
>> connections, as that seems excessive.
> 
> the not very clearly named sigc::trackable::notify_callbacks() gets
> close to this, but is intended to be called from the destructor of a
> trackable or derived type. it will cause all connections to the signals
> of the object it is called for to be dropped. sigc++ keeps track of the
> connections, you see. but note: i do mean *all* connections. you have no
> control over which ones.

What if you use a trackable special for this purpose, bound and hidden?

<code>
#include <iostream>
#include <sigc++/sigc++.h>


void func1()
{
  std::cout << "func1" << std::endl;
}

void func2()
{
  std::cout << "func2" << std::endl;
}

int _tmain(int argc, _TCHAR* argv[])
{
  sigc::signal<void> sig;
  sigc::trackable t;

  {
    sig.connect(sigc::bind(sigc::hide(&func1), sigc::ref(t)));
    sig.emit();
    t.notify_callbacks();
  }
  // does nothing
  sig.emit();

  {
    sig.connect(sigc::bind(sigc::hide(&func2), sigc::ref(t)));
    sig.emit();
    t.notify_callbacks();
  }
  // does nothing
  sig.emit();

  std::cin.get();

  return 0;
}
</code>