class_test.c

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

/* human class (structure)
   This structure has pointers to methods.
 */
typedef struct _human{
  char* _name;
  int _age;

  /* get */
  char* (*get_name)(struct _human* self);
  int (*get_age)(struct _human* self);
  /* set */
  int (*set_name)(struct _human* self, char* name);
  int (*set_age)(struct _human* self, int age);

  /* methods */
  int (*greece)(struct _human* self);
  struct _human* (*delete)(struct _human* self);

} human;

/* return name */
char* _human_get_name(human* self){
  if(!self) return NULL;
  return self->_name;
}

/* return age */
int _human_get_age(human* self){
  if(!self) return -1;
  return self->_age;
}

/* set name
   This method doesn't allow overwrite of name.
 */

int _human_set_name(human* self, char* name){
  if(!self) return 0;
  if(self->_name){
    fprintf(stderr, "WARNING: You can set name once.\n");
    return(1);
  }else{
    self->_name = name;
  }
  return(0);
}

/* set age */
int _human_set_age(human* self, int age){
  if(!self) return(0);
  self->_age = age;
  return(1);
}

/* print greeting message */
int _human_greece(human* self){
  if(!self) return(0);
  printf("Hi, I'm %s.\n", self->get_name(self));
  printf("I'm %d years old.\n", self->get_age(self));
  return(1);
}

/* delete allocated memory */
human* _human_delete(human* self){
  if(!self) return(NULL);
  free(self);
  return NULL;
}

/* constructer */
human* newhuman(char* name, int age){
  /* allocate memory */
  human* self;
  self = malloc(sizeof(human));
  self->_age = -1;
  self->_name = NULL;
  /* link functions */
  self->get_name = _human_get_name;
  self->get_age = _human_get_age;
  self->set_name = _human_set_name;
  self->set_age = _human_set_age;
  self->greece = _human_greece;
  self->delete = _human_delete;
  /* store member functions */
  self->set_name(self, name);
  self->set_age(self, age);
  /* return self */
  return(self);
}

/* main */
int main(void){
  human *taro;
  taro = newhuman("Taro", 18);
  taro->greece(taro);
  taro->set_age(taro, 19);
  taro->greece(taro);
  taro->set_name(taro, "Toshiko");
  taro->greece(taro);
  taro = taro->delete(taro);
  // cannot call
  // taro->get_name(taro);
  return(0);
}