Re: [Dev-C++] Problems with pointers to member functions

[Per W. <pw...@ia...>]

See below.

EMA System        email: pw...@ia...
Per Westermark    web: http://iapetus.neab.net
Vargvaegen 174B   phone: +46 8 410 17 198
S-906 42 Umeaa
Sweden


On Tue, 18 Feb 2003, Tulius Lima wrote:

> Hi Folks,
>
>
>       I've been trying to work with pointers to member functions (after I
> saw the code posted by Japp de Wolff) to implement a finite-state machine
> for a SDL sprite engine.
>
>       After a few bumps I managed to compile the code. But it crashes when
> it runs (when it hits the member function).
>
>       Can anyone tell me please what's wrong with my code?
>
>
>       TIA
>       Tulius Lima
>
> ------------
>
> typedef void (Sprite::*Action)();
>
> class Sprite
> {
> public:
>
>   // operations
>   void moveUp();
>   void moveDown();
>   void moveLeft();
>   void moveRight();
>   void stop();
>   void move();
>
> };
>
>
> int main(int argc, char *argv[])
> {
>   Sprite ship;
>   Action action;
>   Uint8* keys;
>
>   // SDL code omitted
>
>   int done = 0;
>   while (!done)
>   {
>     keys = SDL_GetKeyState(NULL);
>     if ( keys[SDLK_UP] )
>     {
>       action = &Sprite::moveUp;
>     }
>     if ( keys[SDLK_DOWN] )
>     {
>       action = &Sprite::moveDown;
>     }
>     if ( keys[SDLK_LEFT] )
>     {
>       action = &Sprite::moveLeft;
>     }
>     if ( keys[SDLK_RIGHT] )
>     {
>       action = &Sprite::moveRight;
>     }

And what will action be initialized to if none of the four if statements
above are valid?

>
>     (ship.*action)(); // <--- problematic code
>
>     SDL_Flip(screen);
>   }
>
>   // SDL finalization code omitted
>
>   return 0;
> }
> -------------------- end
>
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