C语言多态与继承

 

C语言多态与继承

void *与函数指针、结构体是c语言能实现继承与多态的重要组成部分。

void *：万能的指针

int * 叫做指向整型的指针，而 char * 是指向字符型的指针等等。

而 void *，不要按照通常的命名方式叫它做指向 void 类型的指针，它的正式的名字叫做：可以指向任意类型的指针。

函数指针：指向函数的指针

示例代码：

#include <stdio.h>
#include <stdlib.h>
 
//虚函数表结构
struct base_vtbl
{
    void(*dance)(void *);
    void(*jump)(void *);
};
 
//基类
struct base
{
    /*virtual table*/
    struct base_vtbl *vptr;
};
 
void base_dance(void *this)
{
    printf("base dance\n");
}
 
void base_jump(void *this)
{
    printf("base jump\n");
}
 
/* global vtable for base */
struct base_vtbl base_table =
{
        base_dance,
        base_jump
};
 
//基类的构造函数
struct base * new_base()
{
    struct base *temp = (struct base *)malloc(sizeof(struct base));
    temp->vptr = &base_table;
    return temp;
}
 
 
//派生类
struct derived1
{
    struct base super;
    /*derived members */
    int high;
};
 
void derived1_dance(void * this)
{
    /*implementation of derived1's dance function */
    printf("derived1 dance\n");
}
 
void derived1_jump(void * this)
{
    /*implementation of derived1's jump function */
    struct derived1* temp = (struct derived1 *)this;
    printf("derived1 jump:%d\n", temp->high);
}
 
/*global vtable for derived1 */
struct base_vtbl derived1_table =
{
    (void(*)(void *))&derived1_dance,
    (void(*)(void *))&derived1_jump
};
 
//派生类的构造函数
struct derived1 * new_derived1(int h)
{
    struct derived1 * temp= (struct derived1 *)malloc(sizeof(struct derived1));
    temp->super.vptr = &derived1_table;
    temp->high = h;
    return temp;
}
 
 
 
int main(void)
{
 
    struct base * bas = new_base();
    //这里调用的是基类的成员函数
    bas->vptr->dance((void *)bas);
    bas->vptr->jump((void *)bas);
 
 
    struct derived1 * child = new_derived1(100);
    //基类指针指向派生类
    bas  = (struct base *)child;
 
    //这里调用的其实是派生类的成员函数
    bas->vptr->dance((void *)bas);
    bas->vptr->jump((void *)bas);
    return 0;
}