Re: Function pointer, is this possible?

From:

"Alf P. Steinbach" <alfps@start.no>

Newsgroups:

comp.lang.c++

Date:

Tue, 16 Jun 2009 20:02:56 +0200

Message-ID:

<h18moq$dvj$1@news.eternal-september.org>

* lilith@dcccd.edu:

Hopefully I can describe this in a clear manner.

I've created a button class with private member

(int) (* func) (void);

This is set using

void BTN::SetFunction(int (*fnc)(void))

Style issue: avoid using all uppercase names except for macros.

{
func = fnc;
}

This compiles fine. The problem comes when I use SetFunction to
assign the function I want to run. Under straight forward
circumstances this should compile fine. However, the function I want
to set it to is a public member of another class object, bg of class
Grid.

btnNew.SetFunction ( bg.SetNewMode );

But I get a repremand to

"use '&Grid::SetNewMode' to create a pointer to member"

Does this mean that I can only specify a static function of a class?

With your SetFunction, yes.

The more I think about this I can see why the compiler chokes on this.
Aside from providing discete functions to wrap the call to
bg.SetNewMode() is there any way to use a function pointer with a
non-static function of a class?

Make your SetFunction take a pointer to an event interface:

   struct ClickHandler
   {
       virtual void onClicked() = 0;
   };

   void Button::set( ClickHandler* handler )
   {
       myClickHandler = handler;
   }

If you want to do general event handling check out Boost slots.

Cheers & hth.,

- Alf

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