C++虚拟函数

 1 #include <iostream>
 2 
 3 using namespace std;
 4 
 5 class A{
 6 public:
 7     A();
 8     void f1();
 9     virtual void f2();
10     virtual void f3()=0;
11     virtual ~A();
12 };
13 
14 A::A(){
15     cout<<"construct class A"<<endl;
16 }
17 
18 void A::f1(){
19     cout<<"A : f1()"<<endl;
20 }
21 
22 void A::f2(){
23     cout<<"A : f2()"<<endl;
24 }
25 
26 A::~A(){
27     cout<<"A : ~A()"<<endl;
28 }
29 
30 class B:public A{
31 public:
32     B();
33     void f1();
34     void f2();
35     void f3();
36     virtual ~B();
37 };
38 
39 B::B(){
40     cout<<"construct class B"<<endl;
41 }
42 
43 void B::f1(){
44     cout<<"B : f1()"<<endl;
45 }
46 
47 void B::f2(){
48     cout<<"B : f2()"<<endl;
49 }
50 
51 void B::f3(){
52     cout<<"B : f3()"<<endl;
53 }
54 
55 B::~B(){
56     cout<<"B : ~B()"<<endl;
57 }
58 
59 int main()
60 {
61     cout<<"initialize the A pointer to the B object."<<endl;
62     A *m_j = new B();
63     m_j -> f1();
64     m_j -> f2();
65     m_j -> f3();
66     delete m_j;
67 
68     cout<<"initialize the B pointer to the B object."<<endl;
69     B *pB = new B();
70     pB -> f1();
71     pB -> f2();
72     pB -> f3();
73     delete pB;
74     return 0;
75 }