C++中的虚函数

 1 #include <iostream>
 2 #include <cstring>
 3 
 4 using namespace std;
 5 
 6 class Base{
 7     public:
 8         virtual void func1();
 9         virtual void func2();
10         void func3();
11         void func4();
12 };
13 
14 void Base::func1(){
15     cout<<"Base func1"<<endl;
16 }
17 
18 void Base::func2(){
19     cout<<"Base func2"<<endl;
20 }
21 
22 void Base::func3(){
23     cout<<"Base func3"<<endl;
24 }
25 
26 void Base::func4(){
27     cout<<"Base func4"<<endl;
28 }
29 
30 class Derived1:public Base{
31     public:
32         void func1();//virtual可以省略
33         //char func2(){};错误，虚函数返回类型需要一致
34         void func3();
35         char func4();
36 };
37 
38 void Derived1::func1(){
39     cout<<"Derived1 func1"<<endl;
40 }
41 
42 void Derived1::func3(){
43     cout<<"Derived1 func3"<<endl;
44 }
45 
46 char Derived1::func4(){
47     cout<<"Derived1 func4 can change the return type"<<endl;
48 }
49 
50 class Derived2:public Base{
51     public:
52         void func1();
53 };
54 
55 void Derived2::func1(){
56     cout<<"Derived2 func1"<<endl;
57 }
58 
59 int main(){
60 
61     Base *B;
62     Derived1 De1;
63     B = &De1;
64     B->func1();
65     B->func3();
66     B->func4();
67     De1.func4();
68 
69     Derived2 *pDe2;
70     pDe2 = (Derived2*)&De1;
71     pDe2->func1();
72 
73     return 0;
74 
75 }