simple_factory

#include<string.h>

typedef struct _operate
{
	int a;
	int b;
	int (*getResult)(struct _operate *p);
}Operate;
typedef struct _add
{
	Operate add;
	int c;
}Add;
typedef struct _sub
{
	Operate sub;
	int c;
}Sub;
typedef struct _mul
{
	Operate mul;
	int c;
}Mul;
typedef struct _div
{	
	Operate div;
	int c;
}Div;
int f_add(Operate *p)
{
	return (p->a + p->b);
}
int f_sub(Operate *p)
{
	return (p->a - p->b);
}
int f_mul(Operate *p)
{
	return (p->a * p->b);
}
int f_div(Operate *p)
{
	return (p->a / p->b);
}

Operate *simple_factory(int flag)
{
	Operate *operate = NULL;
	switch(flag)
	{
		case 1:
			operate = (Operate *)malloc(sizeof(Add));
			memset(operate,0,sizeof(Add));
			operate->getResult = f_add;	
			break;
		case 2:	
			operate = (Operate *)malloc(sizeof(Sub));
			memset(operate,0,sizeof(Sub));	
			
			operate->getResult = f_sub;	
			break;
		case 3:	
			operate = (Operate *)malloc(sizeof(Mul));
			memset(operate,0,sizeof(Mul));	
			
			operate->getResult = f_mul;	
			break;
		case 4:	
			operate = (Operate *)malloc(sizeof(Div));
			memset(operate,0,sizeof(Div));	
			
			operate->getResult = f_div;	
			break;
	}
	
	return operate;
}

#include<stdio.h>
#include<stdlib.h>
#include"simpleFactory.c"

/*
Add *ad = NULL;
Operate *op = (Operate *)malloc(sizeof(Add));
ad = (Add *)op  //lower to child

Operate op = NULL;
Add *add = (Add *)malloc(sizeof(Add));
op = (Operate *)add;	//upper to father

*/

/* 1-->'+' 2-->'-' 3-->'x' 4-->'/' */
void main(int args, int argc[])
{
	int ret = 0;
	Add * add = NULL;
	Operate *op = simple_factory(1);
	op->a = 5;
	op->b = 2;

	ret = op->getResult(op);
	printf("ret is %d\n",ret);		
}