http://stackoverflow.com/questions/4112796/are-there-any-design-patterns-in-c

poly.c

/* http://adampetersen.se/Patterns%20in%20C%201.pdf
 * http://adampetersen.se/Patterns%20in%20C%202,%20STATE.pdf
 * http://www.adampetersen.se/Patterns%20in%20C%203,%20STRATEGY.pdf
 * http://www.adampetersen.se/Patterns%20in%20C%204,%20OBSERVER.pdf
 * http://www.adampetersen.se/Patterns%20in%20C%205,%20REACTOR.pdf
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

struct IAnimal {
    void (*eat)(int food);
    void (*sleep)(int secs);
};

struct Cat {
    struct IAnimal _base;
    void (*meow)(void);
};

void cat_eat(int food) { printf("%s: %d\n", __func__, food); };
void cat_sleep(int secs) { printf("%s: %d\n", __func__, secs); };
void cat_meow(void) { printf("%s: meow!\n", __func__); };


struct Cat* CreateACat(void) {
    struct Cat* x = malloc(sizeof (struct Cat));
    x->_base.eat = cat_eat;
    x->_base.sleep = cat_sleep;
    x->meow = cat_meow;

    return x;
}



int main(int argc, char *argv[])
{
	struct IAnimal* pa = (struct IAnimal*) CreateACat();
	pa->eat(42);                       

	((struct Cat*) pa)->meow();        
 	return 0;
}