c++中的动态联编

在c++中的动态联编是通过虚函数来实现，但在调用时 ， 必须用引用、指针才能实现动态联编

例子如下：

指针调用

#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()<
    
     
 
     
     
 
     





 
     

 
 
     
普通变量调用
 
     
<  http://www.2cto.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<