虚函数的默认参数是静态绑定

   1: #include<iostream>

   2: #include<string>

   3: using namespace std;

   4: class Base

   5: {

   6: public:

   7:     virtual void Speak(string str="Base class")

   8:     {

   9:         cout<<"In base clsss ,the default str is "<<str<<endl;

  10:     }

  11: };

  12:  

  13: class Child:public Base

  14: {

  15: public:

  16:     void Speak(string str="child class")

  17:     {

  18:         cout<<"In child class,the default str is "<<str<<endl;

  19:     }

  20: };

  21:  

  22: int main()

  23: {

  24:     Base *pB = new Base();

  25:     Child *pC = new Child();

  26:     pB->Speak();

  27:     pC->Speak();

  28:     pB = new Child();

  29:     pB->Speak();

  30: }