Re: [sigc] Re: [Boost-users] Signals & Slots

[Martin Schulze <martin-ml hippogriff de>]

Am 08.01.2005 12:34:15 schrieb(en) Murray Cumming:
> On Sat, 2005-01-08 at 06:05 -0500, Carl Nygard wrote:
> > On Sat, 2005-01-08 at 09:23 +0100, Murray Cumming wrote:
> > > On Fri, 2005-01-07 at 20:10 -0500, Carl Nygard wrote:
> > > > sigc::connect() -- can it take a function object or
> ptr-to-function or
> > > > must they be wrapped with sigc::ptr_fun() or sigc::mem_fun()?
> > >
> > > You can use a pointer-to-function without using sigc::ptr_fun().
> I
> > > tested that just now.
> > >
> > > A pointer-to-member-function without sigc::mem_fun() would be
> useless
> > > without the object instance.
> >
> > Yeah, but it can assume operator()() if given the address of a
> class
> > object instance, in the case of a function object.  That's what I
> meant
> > by "function object ... without... sigc::mem_fun()"?  Is that
> supposed
> > to work, or is the explicit sigc::mem_fun() required?
>
> Yes, this works:
>
> class foo
> {
>   public:
>   void operator()(int i)
>   {
>     std::cout << "foo(int "<< i << ")" << std::endl;
>   }
> };
>
> int main()
> {
>   sigc::signal<void, int> sig;
>
>   foo instance;
>   sig.connect(instance);
>
>   sig.emit(1);
> }
>
>
> Again, I am surprised. I'm not sure whether I like it, but I guess
> people should be less surprised as they get used to functors.

This is fully intended. Apart from function pointers, signal::connect  
is meant to take any functor object and convert it into a slot object  
implicitly.

Regards,

 Martin