Re: user data in signals

[Daniel Elstner <daniel kitta googlemail com>]

Am Sonntag, den 14.06.2009, 19:14 -0400 schrieb Christopher Harvey:
> I've got a button signal handler, so it takes no parameters. I was
> wondering if there was some way I could send "user data" when the signal
> is connected.

Sure.

> something like this:
> 
> void handlePress(int buttonID) {
>    //I use buttonID here
> }
> 
> int main() {
>    b1.signal_clicked().connect(ptr_fun(handlePress(1)));
>    b2.signal_clicked().connect(ptr_fun(handlePress(2)));
>    b3.signal_clicked().connect(ptr_fun(handlePress(3)));
> }

Make that:

    b1.signal_clicked().connect(sigc::bind(&handlePress, 1)));
    b2.signal_clicked().connect(sigc::bind(&handlePress, 2)));
    b3.signal_clicked().connect(sigc::bind(&handlePress, 3)));

> Doesn't plain gtk support something like this?

Yes it does.  In fact, language bindings in particular make extensive
use of this important feature of the G* APIs. :-)

gtkmm maps GObject signals to sigc++, which is much more powerful and
compile-time type-safe.

--Daniel