虚函数小总结

当在基类中把成员函数定义为虚函数后，其派生类中定义的虚函数必须与基类的虚函数同名，参数的类型、顺序、个数必须一一对应。注：析构函数除外举例为。

#include "iostream.h"
class Base
{
public:
 Base()
 {
  cout<<"construct  in  Base\n";
 }
 virtual ~Base()
 {
  cout<<"destructing Base"<<endl;
 }
protected:
private:
};

class Subclass:public Base
{
public:
 Subclass()
 {
  cout<<"construct in Subclass\n";
 }
 ~Subclass()
 {
  cout<<"destructing Subclass"<<endl;
 }
};
void test (Base *x)
{
 delete x;
}

void main()
{
 cout<<"first\n";
 Base *bc=new Base;
 cout<<"second\n";
 Subclass *sc=new Subclass;
 cout<<"calling test(bc)\n";
 test(bc);
 
 cout<<"calling test(sc)\n";
 test(sc);
 cout<<"end!\n";
}

输出结果为：

first

construct  in  Base

second 

construct in Subclass

calling test(bc)

destructing Base

calling test(sc)

destructing Subclass

destructing Base

end!