c++中的動態聯編

在c++中的動態聯編是通過虛函數來實現，但在調用時 ， 必須用引用、指針才能實現動態聯編

例子如下：

指針調用

#include 

using namespace std;

const double pi = 3.14;

class A
{
public:
    A() {};
    virtual double area() const {return 0.0;}

};

class B:public A
{
public:
    B(double myr)  {R = myr;}
    virtual double area()  const {return pi*R*R;}
private:
    double R;


};


int main()
{

    A *fig;

    B c(3.0);
    cout<<"Area of B is  ";
    fig = &c;
    cout<area()<







普通變量調用
<喎?http://www.Bkjia.com/kf/ware/vc/" target="_blank" class="keylink">vcD4KPHByZSBjbGFzcz0="brush:java;">#include 

using namespace std;

const double pi = 3.14;

class A
{
public:
    A() {};
    virtual double area() const {return 0.0;}

};

class B:public A
{
public:
    B(double myr)  {R = myr;}
    virtual double area()  const {return pi*R*R;}
private:
    double R;


};


int main()
{

    A fig;

    B c(3.0);
    cout<<"Area of B is  ";
    fig = c;
    cout<