C实现面向对象封装、继承、多态

参考资料：

     http://blog.chinaunix.net/uid-26750235-id-3102371.html

     http://www.eventhelix.com/realtimemantra/basics/ComparingCPPAndCPerformance2.htm#.U0jCR7KBR7h

 

说明：

         Shape类为基类，包含typeName，虚函数为求解Shape的周长、面积、析构函数

 

头文件 Cobject.h

#pragma once

/*

*    使用C实现面向对象编程：封装、继承、多态

*/

//基类

struct Shape

{

    char *typeName;

    struct ShapeOps *ops;

};

//基类虚函数指针

struct ShapeOps

{

    float (*OpsArea)(struct Shape* shape);    //求面积

    int (*OpsPerimeter)(struct Shape* shape);    //求周长

    void (*OpsDestory)(struct Shape *shape);    //析构对象

};

//基类的虚函数

float Area(struct Shape *shape);

int Perimeter(struct Shape *shape);

void Destory(struct Shape *shape);

/*********************************************************************************/

//派生类“三角形”triangle

struct Triangle

{

    struct Shape shape;

    int a;

    int b;

    int c;

};

//派生类接口

struct Triangle* TriCreate(int a,int b,int c);

float TriArea(struct Shape *triangle);

int TriPerimeter(struct Shape *triangle);

void TriDestory(struct Shape *triangle);

extern struct ShapeOps TriangleOps;

/*********************************************************************************/

//派生类“矩形” rectangle

struct Rectangle

{

    struct Shape shape;

    int w;

    int h;

};

//派生类接口

struct Rectangle* RectCreate(int w,int h);

float RectArea(struct Shape *rectangle);

int RectPerimeter(struct Shape *rectangle);

void RectDestory(struct Shape *rectangle);

extern  struct ShapeOps RectangleOps;

 

源文件 Cobject.c

#include "Cobject.h"

#include <stdio.h>

#include <stdlib.h>

#include <assert.h>

//基类接口

float Area(struct Shape *shape)

{

    assert(shape != NULL);

    return shape->ops->OpsArea(shape);

}

int Perimeter(struct Shape *shape)

{

    assert(shape != NULL);

    return shape->ops->OpsPerimeter(shape);

}

void Destory(struct Shape *shape)

{

    assert(shape != NULL);

    printf("%s Destory\n",shape->typeName);

    shape->ops->OpsDestory(shape);

}

//Triangle 具体接口实现

struct Triangle* TriCreate(int a,int b,int c)

{

    struct Triangle *tri=(struct Triangle *)(malloc(sizeof(struct Triangle)));

    tri->shape.typeName="Triangle";

    tri->shape.ops=&TriangleOps;

    tri->a=a;

    tri->b=b;

    tri->c=c;

    return tri;

}

float TriArea(struct Shape *shape)

{

    struct Triangle *tri;

    assert(shape != NULL);

    tri=(struct Triangle *)(shape);

    return (float)(tri->a * tri->b * tri->c);

}

int TriPerimeter(struct Shape *shape)

{

    struct Triangle *tri;

    assert( shape != NULL);

    tri=(struct Triangle *)shape;

    return ( tri->a + tri->b + tri->c)/2;

}

void TriDestory(struct Shape *shape)

{

    struct Triangle *tri;

    assert(shape != NULL);

    tri =(struct Triangle *)shape;

    free(tri);

}

struct ShapeOps TriangleOps={TriArea,TriPerimeter,TriDestory};

//Rectangle 具体接口实现

struct Rectangle *RectCreate(int w,int h)

{

    struct Rectangle * rect=(struct Rectangle *)malloc(sizeof(struct Rectangle));

    rect->shape.typeName="Rectangle";

    rect->shape.ops=&RectangleOps;

    rect->w=w;

    rect->h=h;

    return rect;

}

float RectArea(struct Shape *shape)

{

    struct Rectangle *rect;

    assert( shape !=NULL );

    rect=(struct Rectangle *)shape;

    return (float)(rect->h * rect->w );

}

int RectPerimeter(struct Shape *shape)

{

    struct Rectangle *rect;

    assert(shape != NULL );

    rect=(struct Rectangle *)shape;

    return  2*(rect->h + rect->w);

}

void RectDestory(struct Shape *shape)

{

    struct Rectangle *rect;

    assert(shape != NULL);

    rect=(struct Rectangle *)shape;

    free(rect);

}

struct ShapeOps RectangleOps={RectArea,RectPerimeter,RectDestory};

 

测试文件 CobjectTest.cpp

extern "C"{

#include "Cobject.h"

};

#include <iostream>

using namespace std;

int main()

{

    Shape *shape[2];

    //创建Triangle

    shape[0]=(Shape*)TriCreate(1,3,2);

    //创建Rectangle

    shape[1]=(Shape*)RectCreate(2,3);

    for(int i=0;i<2;i++)

    {

        cout<<"Area: "<<Area(shape[i])<<endl;

        cout<<"Perimeter: "<<Perimeter(shape[i])<<endl;

        Destory(shape[i]);

    }

}

 

注意：

       1、C不支持函数重载，以及函数默认参数

       2、头文件中函数名默认为extern

       3、C++调用C函数，使用extern “C”