C++中的虚函数的理解和使用

关于C++中的纯虚函数，使用方法个人理解就像是java中的interface一样，使用规则为 1.在基类中定义虚函数。2.在派生类中通过函数覆盖来定义同名的函数。3.定义基类的指针并调用该函数。

#include "stdafx.h"#include<iostream>using namespace std;const double PI = 3.1415926;class Container{protected:    double radius;public:    Container(double r);//抽象类Container的构造函数    virtual double surface_area() = 0;//纯虚函数surface_area 表面积    virtual double volume() = 0;//纯虚函数volume 体积};Container::Container(double r){    radius = r;}class Sphere:public Container{public:    Sphere(double);    double surface_area();    double volume();};Sphere::Sphere(double r):Container(r){    radius = r;}double Sphere::surface_area(){    return 4 * PI*radius*radius;}double Sphere::volume(){    return (4 / 3)*PI*radius*radius*radius;}class Cylinder :public Container{public:    Cylinder(double,double);    double surface_area();    double volume();private:    double height;};Cylinder::Cylinder(double r,double h) :Container(r){    height = h;    radius = r;}double Cylinder::surface_area(){    return PI*radius*radius * 2 + 2 * PI*radius*height;}double Cylinder::volume(){    return PI*radius*radius*height;}class Cube :public Container{public:    Cube(double);    double surface_area();    double volume();};Cube::Cube(double r) :Container(r){    radius = r;}double Cube::surface_area(){    return 6 * radius;}double Cube::volume(){    return radius*radius*radius;}int main(){    Container *s = new Sphere(5.0);    Container *c = new Cylinder(5.0,6.0);    Container *cube = new Cube(6.0);    cout << "计算边长为6.0的正方体、半径为5.0的球体，以及半径为5.0和高为6.0的圆柱体的表面积和体积." << endl;    cout << "球体表面积为： " << s->surface_area()<<endl;    cout << "球体体积为： " << s->volume()<<endl;    cout << "圆柱体表面积为： " << c->surface_area() << endl;    cout << "圆柱体体积为： " << c->volume() << endl;    cout << "正方体表面积为： " << cube->surface_area() << endl;    cout << "正方体体积为： " << cube->volume() << endl;    system("pause");    return 0;}