Re: signals with parameters

[Bob Caryl <bob fis-cal com>]

Andreas Volz wrote:

> Hi,
>
> I've a window class which creates some HScale widgets based on a
> saved file. So I create them dynamic with new and store the pointers in
> a std::vector. This works great, but I could only connect all HScale
> widgets to one callback function:
>
>      hscale->signal_value_changed ().connect (sigc::mem_fun (*this,
>          &Application::on_target_hscale_changed));
>
> In this callback I like to get the correct HScale widget pointer whose
> value was changed. I found this in docs:
>
> http://libsigc.sourceforge.net/libsigc2/docs/manual/html/ch02s03.html
>
> This reads like the stuff I need, but how could I use this with HScale?
> Need I to derivate HScale and add this new signal with parameters? How
> how could I do this?
>
> regards
> Andreas
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>
>  
Hi Andreas,

use sigc::bind to do this:

First prototype Application::on_target_hscale_changed with a gint as its 
formal calling parameter.  then make your signal connection call look 
like the following:

   
hscale->signal_value_changed().connect(sigc::bind<gint>(sigc::mem_fun(*this,&Application::on_target_hscale_changed),i));

where "i" is the zero based index of your derived hscale object in your 
std::vector. 

Now, when Application::on_target_hscale_changed  is called when 
signal_value_changed is emitted, it will be supplied with the value of 
"i" as its formal parameter thereby letting you know which hscale 
emitted the signal.

Cheers,
Bob Caryl