1 class BaseClass
2 {
3 public:
4 int public_int;
5 private:
6 int private_int;
7 protected:
8 int protected_int;
9 };
10
11 class DerivedClass :public BaseClass {
12 public:
13 void UsePublicInt()
14 {
15 public_int = 1; //正确
16 }
17 void UserPrivateInt()
18 {
19 private_int = 1;//错误:成员 BaseClass::private_int不可访问
20 }
21 void UserProtectedInt()
22 {
23 protected_int = 1; //正确
24 }
25 };
26
27 //protected 对ProtectedDerivedClass的派生类和用户和友元函数产生影响,对ProtectedDerivedClass自身的成员函数无影响
28 class ProtectedDerivedClass :protected BaseClass {
29 public:
30 void UsePublicInt()
31 {
32 public_int = 1; //正确 BaseClass::public_int是公有的
33 }
34 void UserPrivateInt()
35 {
36 private_int = 1;//错误:成员 BaseClass::private_int不可访问
37 }
38 void UserProtectedInt()
39 {
40 protected_int = 1; //正确
41 }
42 };
43
44 int main()
45 {
46 BaseClass baseclass;
47 baseclass.public_int; //正确
48 baseclass.protected_int; //错误:成员 BaseClass::protected_int不可访问
49 baseclass.private_int; //错误:成员 BaseClass::private_int不可访问
50
51 DerivedClass derivedclass;
52 derivedclass.public_int; //正确
53 derivedclass.protected_int; //错误:成员 BaseClass::protected_int不可访问
54 derivedclass.private_int; //错误:成员 BaseClass::private_int不可访问
55
56 ProtectedDerivedClass protectedderivedclass;
57 protectedderivedclass.public_int = 1;//错误:成员 BaseClass::public_int不可访问 原因 ProtectedDerivedClass :protected DerivedClass,对ProtectedDerivedClass的用户而言public_int是protectd,所以无法访问
58 protectedderivedclass.protected_int; //错误:成员 BaseClass::protected_int不可访问
59 protectedderivedclass.private_int; //错误:成员 BaseClass::private_int不可访问
60 }
