纯C实现面向对象之接口编程

创建如下文件目录：

Shape.h

#include <stdlib.h>
//接口
#ifndef Interface
#define Interface struct
#endif
//类
#ifndef Class
#define Class struct
#endif
//SHAPE_H_
#ifndef SHAPE_H_
#define SHAPE_H_
//抽象形状类
Class Shape;
typedef Class Shape * p_shape;
//抽象形状类声明
Class Shape
{
    int edge;
    int (*getEdge)(p_shape shape);
    int (*calcArea)(p_shape shape);
};

//形状类构造函数
p_shape Shape(int edge);
//形状类析构函数
void _Shape(void * shape);
//形状类实例方法
int Shape_getEdge(p_shape shape);
//形状类抽象方法，返回-1，表示未实现
int Shape_calcArea(p_shape shape);

#endif /* SHAPE_H_ */

Shape.c

#include "Shape.h"

p_shape Shape(int edge)
{
    p_shape obj = (p_shape) malloc(sizeof(Class Shape));
    obj->edge = edge;
    obj->getEdge = Shape_getEdge;
    obj->calcArea = Shape_calcArea;
    return obj;
}

void _Shape(void * obj)
{
    if (NULL != obj)
    {
        free(obj);
    }
}

int Shape_getEdge(p_shape shape)
{
    return shape->edge;
}

int Shape_calcArea(p_shape shape)
{
    return -1;
}

Triangle.h

#include "Shape.h"

#ifndef TRIANGLE_H_
#define TRIANGLE_H_
//三角形类
Class Triangle;
typedef Class Triangle * p_triangle;
//三角形类声明
Class Triangle
{
    int bottom;
    int height;
    p_shape super;
    int (*getEdge)(p_triangle triangle);
    int (*calcArea)(p_triangle triangle);
};

//三角形类构造函数
p_triangle Triangle(int bottom, int height);
//三角形类析构函数
void _Triangle(void * triangle);
//三角形类实例方法
int Triangle_getEdge(p_triangle triangle);
//三角形类实例方法，重写父类同名方法
int Triangle_calcArea(p_triangle triangle);

#endif /* TRIANGLE_H_ */

Triangle.c

#include "Shape.h"
#include "Triangle.h"

p_triangle Triangle(int bottom, int height)
{
    p_triangle obj = (p_triangle) malloc(sizeof(Class Triangle));
    obj->bottom = bottom;
    obj->height = height;
    obj->super = Shape(3);
    obj->getEdge = Triangle_getEdge;
    obj->calcArea = Triangle_calcArea;
    return obj;
}

void _Triangle(void * triangle)
{
    if (NULL != triangle)
    {
        free(triangle);
    }
}

int Triangle_getEdge(p_triangle triangle)
{
    return triangle->super->edge;
}

int Triangle_calcArea(p_triangle triangle)
{
    return triangle->bottom * triangle->height / 2;
}

Rectangle.h

#include "Shape.h"
#ifndef RECTANGLE_H_
#define RECTANGLE_H_
//矩形类
Class Rectangle;
typedef Class Rectangle * p_rectangle;

//矩形类声明
Class Rectangle
{
    int bottom;
    int height;
    p_shape super;
    int (*getEdge)(p_rectangle rectangle);
    int (*calcArea)(p_rectangle rectangle);
};

//矩形类构造函数
p_rectangle Rectangle(int bottom, int height);
//矩形类析构函数
void _Rectangle(void * rectangle);
//矩形类实例方法
int Rectangle_getEdge(p_rectangle rectangle);
//矩形类实例方法，重写父类同名方法
int Rectangle_calcArea(p_rectangle rectangle);

#endif /* RECTANGLE_H_ */

Rectangle.c

#include "Shape.h"
#include "Rectangle.h"

p_rectangle Rectangle(int bottom, int height)
{
    p_rectangle obj = (p_rectangle) malloc(sizeof(Class Rectangle));
    obj->bottom = bottom;
    obj->height = height;
    obj->super = Shape(4);
    obj->getEdge = Rectangle_getEdge;
    obj->calcArea = Rectangle_calcArea;
    return obj;
}

void _Rectangle(void * rectangle)
{
    if (NULL != rectangle)
    {
        free(rectangle);
    }
}

int Rectangle_getEdge(p_rectangle rectangle)
{
    return rectangle->super->edge;
}

int Rectangle_calcArea(p_rectangle rectangle)
{
    return rectangle->bottom * rectangle->height;
}

Main.c

#include "Shape.h"
#include "Triangle.h"
#include "Rectangle.h"
#include <stdio.h>

int main()
{
    p_triangle triangle = Triangle(4, 5);
    printf("%d
", triangle->getEdge(triangle));
    printf("%d
", triangle->calcArea(triangle));
    _Triangle(triangle);

    p_rectangle rectangle = Rectangle(4, 5);
    printf("%d
", rectangle->getEdge(rectangle));
    printf("%d
", rectangle->calcArea(rectangle));
    _Rectangle(rectangle);

    return 0;
}

编译运行,结果如下: