C语言面向对象的封装、继承和多态的思想

#include <stdio.h>#include <stdlib.h>#define Jicheng#define Fengzhuang#define Duotai/*思想为结构体的嵌套*/#ifdef Jicheng   struct jichengfirst { int num;};struct jichengsecond { double tw;};struct jichengthird {   //继承jichengfirst和jichengsecond两个结构体 int mine; struct jichengfirst first; struct jichengsecond second;};#endif/*思想为结构体的嵌套*/#ifdef Fengzhuang    struct fengzhuangbase {   //需要封装的结构体 int base;};struct fengzhuang {    //封装 struct fengzhuangbase *base;};int constructor(struct fengzhuang *f) //建立封装了的结构体{ f->base = (fengzhuangbase *)malloc(sizeof(fengzhuangbase)); if (!f->base)  return -1; return 0;}int get(struct fengzhuang *f) //获得封装结构体中数据{ return f->base->base;}void set(struct fengzhuang *f,int data)  //数据写入封装结构体{ f->base->base = data;}void destructor(struct fengzhuang *f) //删除封装了的结构体{ free(f->base);}#endif/*思想为结构体的内存布局，即结构体内每个域的内存位置是按照定义的顺序从低地址往高地址顺序存放的*/#ifdef Duotai/*获得结构体中的内部对象*/#define offset_of(type,number) \ ((unsigned long) (&((type *)0)->number))#define container_of(ptr,type,number) \ ((type *)((unsigned long)(ptr)-offset_of(type,number)))/*主类型*/struct shape { char *name; struct shape_operations * opt;};struct shape_operations { void (*Draw)(struct shape *);};/*三角形*/struct triangle { int a,b,c; struct shape base;};static void draw_triangle(struct shape *t){ struct triangle* self = container_of(t,struct triangle,base); printf("draw a %s: %d\t%d\t%d\n", t->name, self->a, self->b, self->c);}static struct shape_operations triangle_operations = { draw_triangle,};void triangle_constructor(struct triangle * t,int a,int b,int c){ t->a=(a>0) ? a : 1; t->b=(b>0) ? b : 1; t->c=(c>0) ? c : 1; t->base.name = "triangle"; t->base.opt = &triangle_operations;}/*正方形*/struct square {    int e;    struct shape base;}; static void draw_square(struct shape* s){    struct square* self = container_of(s, struct square, base);    printf("draw a %s: e = %d\n", s->name, self->e);} static struct shape_operations square_operations = {    draw_square,}; void square_constructor(struct square* s, int e){    s->e = (e > 0) ? e : 1;    s->base.name = "square";    s->base.opt = &square_operations;}/*输出函数*/void DrawShape(struct shape * s){ s->opt->Draw(s);}#endif 测试：int main(){ triangle t; triangle_constructor(&t,2,2,2); DrawShape(&t.base); square s; square_constructor(&s,4); DrawShape(&s.base); return 0;}