Re: [Boost-Users] Using Bind on Signals

30 May 2003

      Darren Vincent Hart wrote:
[...]
...
struct widget
{
boost::signal sig;
boost::signal keypress;
bool test()
{
cout << "widget::test() - sig empty: " << (sig.empty() ? "true" :
"false") << endl;
sig();
return true;
}
};
[...]
// bind to a widget signal handler, BROKEN
//handler<bool> handler_b( boost::bind<bool>(&widget::sig, &widget_a)
);  // <-- Broken
[...]
// store the function object returned by binding a widget signal,
BROKEN
//boost::function fp = boost::bind(&widget::sig, &widget_a);
// <-- BROKEN
// executre the functor returned by binding a widget signal, BROKEN
// (builds, but doesn't really call widget_a.sig())
boost::bind(&widget::sig, &widget_a)();  // <-- Test if binding works
at all, it doesn't
bind(&widget::sig, &widget_a)() gets you a reference to widget_a->sig since
&widget::sig is a data member. You still need to call it.

bool call(signal const & s) { return s(); }

bind(call, bind(&widget::sig, &widget_a)) ();

will probably do what you want.

You can use apply<> from  instead of 'call':

bind(apply<bool>(), bind(&widget::sig, &widget_a)) (); // should call
widget_a->sig

HTH

Re: [Boost-Users] Using Bind on Signals

Peter Dimov