一.單繼承的對象模型

class Car{public:    virtual void func1()    {        cout << "Car::func1()" << endl;    }    virtual void func2()    {        cout << "Car::func2()" << endl;    }PRotected:    int _c;//種類};class Bike :public Car{public:    virtual void func1()    {        cout << "Bike::func1()" << endl;    }    virtual void func2()    {        cout << "Bike::func2()" << endl;    }    virtual void func3()    {        cout << "Bike::func3()" << endl;    }protected:    int _b;//自行車數(shù)量};int main(){    Car c;    Bike b;    system("pause");    return 0;}通過這種表我們對單繼承有個初步的了解，可以看道派生類Bike::func1重寫（覆蓋）了父類Car::func1，覆蓋了虛表函數(shù)的位置。但是我們細(xì)心發(fā)現(xiàn)，派生類Bike::func3消失了。我們可以打印函數(shù)的地址打開內(nèi)存看個究竟：
class Car{public:    virtual void func1()    {        cout << "Car::func1()" << endl;    }    virtual void func2()    {        cout << "Car::func2()" << endl;    }protected:    int _c;//種類};class Bike :public Car{public:    virtual void func1()    {        cout << "Bike::func1()" << endl;    }    virtual void func2()    {        cout << "Bike::func2()" << endl;    }    virtual void func3()    {        cout << "Bike::func3()" << endl;    }protected:    int _b;//自行車數(shù)量};typedef void(*FUNC) ();void PrintfVtable(void *_vfptr){    int *Vtable = (int *)_vfptr;    printf("虛表的地址Vtable:0x%x/n",Vtable);    for (size_t i = 0; Vtable[i] != 0; ++i)    {        printf("第%d個虛函數(shù)的地址:0x%x/n", i, Vtable[i]);        FUNC f = (FUNC)Vtable[i];        f();    }}int main(){    Car c;    Bike b;    int *Vtable1 = (int*)(*((int*)&c));    int *Vtable2 = (int*)(*((int*)&b));    PrintfVtable(Vtable1);    PrintfVtable(Vtable2);    system("pause");    return 0;}我們畫一下它的對象模型:
三.菱形對象
class AA{public:    virtual void fun1()    {        cout << "AA::fun1()" << endl;    }    virtual void funA()    {        cout << "AA::funA()" << endl;    }public:    int _aa;};class BB :public AA{public:    virtual void fun1()    {        cout << "BB::funB()" << endl;    }    virtual void funB()    {        cout << "BB::funB()" << endl;    }public:    int _bb;};class CC :public AA{public:    virtual void fun1()    {        cout << "CC::fun1()" << endl;    }    virtual void funC()    {        cout << "CC::funC()" << endl;    }public:    int _cc;};class DD :public BB,public CC{public:    virtual void fun1()    {        cout << "DD::fun1()" << endl;    }    virtual void funD()    {        cout << "DD::funD()" << endl;    }public:    int _dd;};typedef void(*FUNC)();void PrintfVtable(void *_vfptr){         int*Vtable = (int *)_vfptr;        printf("虛表的地址Vtable:0x%x/n",Vtable);        for (size_t i = 0; Vtable[i] != 0; ++i)        {            printf("第%d個虛函數(shù)的地址:0x%x/n", i, Vtable[i]);            FUNC f = (FUNC)Vtable[i];            f();        }   }int main(){    DD d;    d.BB::_aa = 0;    d.CC::_aa = 1;    d._bb  = 2;    d._cc = 3;    d._dd = 4;    int *Vtable1 = (int*)(*((int*)&d));    PrintfVtable(Vtable1);    system("pause");    return 0;}通過上面我們很清楚的看到有兩個虛表分別存放虛函數(shù)的地址，第一個存放派生類DD::fun1()的地址和AA::funA();第二個虛函數(shù)存放AA::funA()的地址。這里面就出現(xiàn)菱形繼承的問題二義性和數(shù)據(jù)的冗余的問題。通過觀察內(nèi)存看到。
三.菱形虛擬繼承
在public前面加上關(guān)鍵字virtual:class AA{public:    virtual void fun1()    {        cout << "AA::fun1()" << endl;    }    virtual void funA()    {        cout << "AA::funA()" << endl;    }public:    int _aa;};class BB :virtual public AA{public:    virtual void fun1()    {        cout << "BB::funB()" << endl;    }    virtual void funB()    {        cout << "BB::funB()" << endl;    }public:    int _bb;};class CC :virtual public AA{public:    virtual void fun1()    {        cout << "CC::fun1()" << endl;    }    virtual void funC()    {        cout << "CC::funC()" << endl;    }public:    int _cc;};class DD :public BB,public CC{public:    virtual void fun1()    {        cout << "DD::fun1()" << endl;    }    virtual void funD()    {        cout << "DD::funD()" << endl;    }public:    int _dd;};typedef void(*FUNC)();void PrintfVtable(void* _vptr){    int *Vtable = (int*)_vptr;    printf("虛表的地址)0x%x/n", Vtable);        for (size_t i = 0; Vtable[i] != 0; ++i)        {            printf("第%d個虛函數(shù)的地址:0x%x/n", i, Vtable[i]);            FUNC f = (FUNC)Vtable[i];            f();        }   }int main(){    DD d;    d.BB::_aa = 0;    d.CC::_aa = 1;    d._bb  = 2;    d._cc = 3;    d._dd = 4;    int *Vtable = (int*)(*((int*)&d));    PrintfVtable(Vtable);    system("pause");    return 0;}前面我們也知道菱形繼承就是多繼承的一種，看到上面也發(fā)現(xiàn)多繼承與單繼承的區(qū)別，至于多繼承的模型我們下次繼續(xù)。。。