struct-example.c

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

struct example {
  void (*add)(struct example *, int);
  void (*show)(struct example *);
  int number;
};

void example_add(struct example *this, int n)
{
  this->number += n;
}

void example_show(struct example *this)
{
  printf("this->number = %d\n", this->number);
}

struct example *new_example(int n)
{
  struct example *new = malloc( sizeof (struct example) );
  
  new->add    = example_add;
  new->show   = example_show;
  new->number = n;

  return new;
}

void destroy_example(struct example *obj)
{
  free(obj);
}

int main(void)
{
  struct example *test = new_example(5);
  
  test->add(test, 4);
  test->show(test);
  
  destroy_example(test);
  return 0;
}