虚函数和多态的基本概念

虚函数基本概念

多态的两种表现形式

其一

其二

多态的作用

注：多态的作用将在后两节得到体现

代码实例

#include <bits/stdc++.h>
using namespace std;
class A
{
public:
    virtual void print(void) { cout << "Class A::Print" << endl; };
};
class B : public A
{
public:
    virtual void print(void) { cout << "Class B::Print" << endl; };
};
class D : public A
{
public:
    virtual void print(void) { cout << "Class D::Print" << endl; };
};
class E : public B
{
public:
    virtual void print(void) { cout << "Class E::Print" << endl; };
};
int main(void)
{
    A a;
    B b;
    D d;
    E e;
    A *pa = &a;
    B *pb = &b;
    D *pd = &d;
    E *pe = &e;
    pa->print();
    pa = pb;
    pb->print();
    pa = pd;
    pa->print();
    pa = pe;
    pa->print();
    return 0;
}
/*
Class A::Print
Class B::Print
Class D::Print
Class E::Print
*/