#include <iostream>

using namespace std;
/* 每個類都有一張虛方法表，當基類為虛方法，而派生類重載了虛方法，
* 則虛方法表中的基類方法被派生類替換
*/
class AClass{
??? public:
??????? AClass(){
??????????? cout << this << " 基類構造" << endl;
??????? }
??????? virtual ~AClass(){
??????????? cout << this << " 基類析構" << endl;
??????? }
??????? void Amothod1(){
??????????? cout << "基類方法1" << endl;}
??????? virtual void Amothod2(){
??????????? cout << "基類方法2" << endl;}
??????? void Amothod3(){
??????????? cout << "基類方法3" << endl;}
};
class BClass:public AClass{
??? public:
??????? BClass(){
??????????? cout << this << " 派生類構造" << endl;
??????? }
??????? virtual ~BClass(){
??????????? cout << this << " 派生類析構" << endl;
??????? }
??????? void Amothod1(){
??????????? cout << "派生類方法1" << endl;}
??????? void Amothod2(){
??????????? cout << "派生類方法2" << endl;}
};

int main()
{
??? AClass * a = new AClass;// 基類指針操縱基類實例
??? a->Amothod1();// 調用基類方法1
??? a->Amothod2();// 調用基類方法2
??? a->Amothod3();// 調用基類方法3
??? delete a;
??? cout << "***虛方法不影響指向基類實例的基類指針***" << endl;

??? AClass * a1 = new BClass;// 基類指針操縱派生類實例
??? a1->Amothod1();// 調用基類方法1
??? a1->Amothod2();// 調用派生類方法2
??? a1->Amothod3();// 調用基類方法3
//??? ((BClass *)a1)->Amothod1();// 等效于b->Amothod1();
//??? ((BClass *)a1)->Amothod2();// 等效于b->Amothod2();
//??? ((BClass *)a1)->Amothod3();// 等效于b->Amothod3();
??? delete a1;
??? cout << "***虛方法影響指向派生類實例基類指針***" << endl;

??? BClass * b = new BClass;// 派生類指針操縱派生類實例
??? b->Amothod1();// 調用派生類方法1
??? b->Amothod2();// 調用派生類方法2
??? b->Amothod3();// 調用基類方法3
//??? ((AClass *)b)->Amothod1();// 等效于a1->Amothod1();
//??? ((AClass *)b)->Amothod2();// 等效于a1->Amothod2();
//??? ((AClass *)b)->Amothod3();// 等效于a1->Amothod3();
??? delete b;
??? cout << "***如果不重載基類公共方法，將直接調用基類方法***" << endl;

??? return 0;
}

總結

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