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Function Pointers

Started by Reactivore Jul 5, 2000 at 10:37 AM 4 replies 300+ views

Original Post

Jul 5, 2000 at 10:37 AM

Howdy, folks. Just here to ask a simple question. I''m creating a class for a button in DX, and the way I would like to do it would be to pass in a defined function to operate the button. It looks something like this. typedef class BUTTON { void *Execute; inline void BUTTON(); } Button; inline void GUI::BUTTON::BUTTON(void *Func()) { Execute = Func; } Is this basically how you do it. How could I get the code to work. Thanks for the help.

DanJames

Jul 5, 2000 at 12:07 PM

Here''s an example of pointers to functions in C:

int somefunc() { printf("in somefunc"); }
int anotherfunc() { printf("in anotherfunc"); }

void main() {

int (*func)();

func = somefunc;
func();

func = anotherfunc;
func();

}

If, for example, somefunc and anotherfunc took one parameter, (an int for example), the function-pointer would be declared as:

int (*func)(int);

DeltaVee

Jul 5, 2000 at 1:11 PM

uh...... C++ right?

why dont you DERIVE a class from your base class

    

class Button
{

 Button();
 virtual ~Button()

 virtual void Execut(void ) = 0;
};

class MyButton1 : public Button
{
 MyButton1();
 virtual ~MyButton1();

 virtual void Execute(void ); // implement this function

};

class AnotherButton : public Button
{
 AnotherButton();
 ~AnotherButton();

 virtual void Execute(); // implement this function

}

// yada yada yada ......

If your going to use a language you might as well use its features instead of re-inventing them.

--------------------------
Carpe Diem

Reactivore

Author

Reactivore

Jul 5, 2000 at 2:10 PM

Hey, thanks, guys. Your advice has been invaluable to the development of my project. Everything in the area of function pointers is good to go!

Kylotan

Mod

3,487

Kylotan

Jul 6, 2000 at 11:08 AM

quote:
Original post by DeltaVee

uh...... C++ right?

why dont you DERIVE a class from your base class

You might want 2 buttons to look different and yet do the same thing (toolbar and menu item, perhaps?). You might want there to be a totally different way of accessing the function too (macros, scripting?) You might want to change the functionality of a button at runtime (customisable interface?) So it makes sense to keep them seperate like this. I would do it the way Anonymous did though, which emphasises that Buttons only take a certain type of function.

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