C++中多态总结

一. 多态的概念

同一事物，在不同场景下的多种形态

例如：“*”在不同场景下的形态

 int* p=&a;//指针 *p;//解引用 a*b;//乘号

二.多态的分类

1.静态多态：编译器在编译期间完成的，编译器根据函数实参的类型(可能会进行隐式类型转换)，可推断出要调用那个函数，如果有对应的函数就调用该函数，否则出现编译错误。

int Add(int a,int b){   return a+b;}float Add(int a,int b)   return a+b;}int main(){   cout<<Add(10,20)<<end1;   cout<<Add(3.14f,5.6f)<<end1;   return 0;}

2.动态多态：在程序执行期间(非编译期)判断所引用对象的实际类型，根据其实际类型调用相应的方法。

class WashRoom{public: void GoToManWashRoom(){    cout << "Man-->Please Left" << endl;}        void GoToWomanWashRoom()        {            cout << "Woman-->Please Right" << endl;        }};class Person{public: virtual void GoToWashRoom(CWashRoom & _washRoom) = 0;};class Man :public Person{public: virtual void GoToWashRoom(WashRoom & washRoom){    washRoom.GoToManWashRoom();}};};class Woman :public Person{public:    virtual void GoToWashRoom(WashRoom & washRoom)    {        washRoom.GoToWomanWashRoom();    }};void FunTest(){    WashRoom washRoom;    for (int iIdx = 1; iIdx <= 10; ++iIdx)    {        Person* pPerson;        int iPerson = rand() % iIdx;        if (iPerson & 0x01)            pPerson = new Man;        else            pPerson = new Woman;        pPerson->GoToWashRoom(washRoom);        delete pPerson;        pPerson = NULL;                Sleep(1000);    }

三. 动态多态的实现条件

1.基类中必须有虚函数；

class Base{public:    virtual void FunTest1(int _iTest){ cout << "Base::FunTest1()" << endl; }    void FunTest2(int _iTest){ cout << "Base::FunTest2()" << endl; }    virtual void FunTest3(int _iTest1){ cout << "Base::FunTest3()" << endl; }    virtual void FunTest4(int _iTest){ cout << "Base::FunTest4()" << endl; }};class Derived :public Base{public:    virtual void FunTest1(int _iTest){ cout << "Derived::FunTest1()" << endl; }    virtual void FunTest2(int _iTest){ cout << "Derived::FunTest2()" << endl; }    void FunTest3(int _iTest1){ cout << "Derived::FunTest3()" << endl; }    virtual void FunTest4(int _iTest1, int _iTest2)        virtual void FunTest4(int _iTest1, int _iTest2)    {        cout << "Derived::FunTest4()" << endl;    }};int main(){    Base* pBase = new Derived;    pBase->FunTest1(0);    pBase->FunTest2(0);    pBase->FunTest3(0);    pBase->FunTest4(0);    pBase->FunTest4(0, 0);    return 0;}

2.通过基类类型的引用或者指针调用虚函数；

四.多态的实现原理

a、编译时多态性（静态多态）：通过重载函数实现

b、运行时多态性（动态多态）：通过虚函数实现。