Re: Function pointer, is this possible?

"Alf P. Steinbach" <>
Tue, 16 Jun 2009 20:02:56 +0200

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

  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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