1、檔案cls.h
標頭檔案cls.h實現了基類Base1、Base2，和子類Derived1、Derived2。

#pragma once
#include <iostream>
using namespace std;

class Base1
{
public:
    Base1() { cout << "Constrution Base1" << endl; }
    //~Base1() { cout << "Destrution Base1" << endl; }

    virtual ~Base1() { cout
 
 << "Destrution Base1" << endl; }

    virtual void f() { cout << "Base1::f" << endl; }

    virtual void g() { cout << "Base1::g" << endl; }

    virtual void h() { cout << "Base1::h" << endl; }

    void func(){ cout << "Base1::func" << endl; }
};

class
 
 Base2
{
public:
    Base2() { cout << "Constrution Base2" << endl; }
    //~Base2() { cout << "Destrution Base2" << endl; }

    virtual ~Base2() { cout << "Destrution Base2" << endl; }

    virtual void f() { cout << "Base2::f" << endl; }

    virtual void
 
 g() { cout << "Base2::g" << endl; }

    virtual void h() { cout << "Base2::h" << endl; }

    void func() { }
};

class Derived1 :public Base1
{
public:
    Derived1() { cout << "Constrution Derived1" << endl; }
    ~Derived1() { cout << "Destrution Derived1" << endl; }

    virtual void f() { cout << "Derived1::f" << endl; }   // virtual可寫可不寫

    virtual void g1() { cout << "Derived1::g1" << endl; }

    virtual void h1() { cout << "Derived1::h1" << endl; }

    void func() { cout << "Derived1::func" << endl; }

};

class Derived2 :public Base2, public Base1
{
public:
    Derived2() { cout << "Constrution Derived2" << endl; }
    ~Derived2() { cout << "Destrution Derived2" << endl; }

    virtual void f()  { cout << "Derived2::f" << endl;  }

    virtual void g1() { cout << "Derived2::g1" << endl; }

    virtual void h1() { cout << "Derived2::h1" << endl; }
};

2、主函式
測試函式的派生、虛擬函式重寫、過載等示例。

#include "cls.h"

int main()
{
    Base1 b1;
    Base2 b2;
    Derived1 d1;
    Derived2 d2;
    // 大小與函式列表有關
    cout << "sizeof(Base1) = " << sizeof(Base1) << " sizeof(b1) = " << sizeof(b1) << endl;
    cout << "sizeof(Base2) = " << sizeof(Base2) << " sizeof(b2) = " << sizeof(b2) << endl;
    cout << "sizeof(Derived1) = " << sizeof(Derived1) << " sizeof(d1) = " << sizeof(d1) << endl;
    cout << "sizeof(Derived2) = " << sizeof(Derived2) << " sizeof(d1) = " << sizeof(d1) << endl;

    Derived1 d;  // d 能直接呼叫Derived1的所有函式、Base1的非虛擬函式，間接呼叫base1的虛擬函式
    d.f();        // Derived::f
    d.g1();       // Derived::g1
    d.Base1::f(); // Base1::f 
    d.func();

    Derived1 *d = new Derived1(); // 同上
    d->f();          // Derived::f
    d->g1();         // Derived::g1
    d->Base1::f();   // Base1::f
    d->func();       // Derived1::func   過載
    d->Base1::func();// Base1::func      間接呼叫，顯示呼叫

    Base1 *b = new Derived1(); // b 只能呼叫Base1的函式，但是虛擬函式會被動態繫結
    b->f();     // Derived1::f 
    b->g();     // Base1::g
    b->func();  // Base1::func

    Base1 *b = new Base1(); // 顯然只能呼叫base1的函式
    b->f();   // Base1::f
    b->g();   // Base1::g
    b->func();// Base1::func


    Base1 *b = new Base1(); 
    delete b; // 不論基類解構函式是否為虛擬函式，都會執行函式體

    Base1 *b = new Derived1(); 
    delete b; // 當基類解構函式為虛時，才會析構父類;    否則，只執行基類的解構函式

    Derived1 *d = new Derived1();
    delete d;   // 不論基類解構函式是否為虛擬函式，都會執行函式體



    Derived2 d2;//直接呼叫Derived2的函式，間接呼叫父類函式
    d2.f();         // Derived2::f
    d2.Base1::f();  // Base1::f
    d2.Base2::f();  // Base2::f

    Derived2 *d2 = new Derived2();//直接呼叫Derived2的函式，間接呼叫父類函式
    d2->f();        // Derived2::f
    d2->Base1::f(); // Base1::f
    d2->Base2::f(); // Base2::f
    delete d2;

    Base1 *d2 = new Derived2();// 呼叫base1的函式和Derived2重寫的函式，
    d2->f();            // 子類重寫 Derived2::f
    d2->Base1::f();   // 間接呼叫父類虛擬函式 Base1::f    
    d2->g();            // 直接呼叫父類虛擬函式 Base1::g    
    d2->func();     // 直接呼叫父類非虛擬函式 Base1::func
    delete d2;        //其中一個父類解構函式必須為虛擬函式

    return 0;
}