C++中public,protected,private的理解

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 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; //正確16     }17     void UserPrivateInt()18     {19         private_int = 1;//錯誤:成員 BaseClass::private_int不可訪問20     }21     void UserProtectedInt()22     {23         protected_int = 1; //正確 24     }25 };26 27 //protected 對ProtectedDerivedClass的衍生類別和使用者和友元函數產生影響,對ProtectedDerivedClass自身的成員函數無影響28 class ProtectedDerivedClass :protected BaseClass {29 public:30     void UsePublicInt()31     {32         public_int = 1; //正確 BaseClass::public_int是公有的33     }34     void UserPrivateInt()35     {36         private_int = 1;//錯誤:成員 BaseClass::private_int不可訪問37     }38     void UserProtectedInt()39     {40         protected_int = 1; //正確 41     }42 };43 44 int main()45 {46     BaseClass baseclass;47     baseclass.public_int; //正確48     baseclass.protected_int; //錯誤:成員 BaseClass::protected_int不可訪問49     baseclass.private_int; //錯誤:成員 BaseClass::private_int不可訪問50 51     DerivedClass derivedclass;52     derivedclass.public_int;   //正確53     derivedclass.protected_int; //錯誤:成員 BaseClass::protected_int不可訪問54     derivedclass.private_int; //錯誤:成員 BaseClass::private_int不可訪問 55 56     ProtectedDerivedClass protectedderivedclass;57     protectedderivedclass.public_int = 1;//錯誤:成員 BaseClass::public_int不可訪問 原因 ProtectedDerivedClass :protected DerivedClass,對ProtectedDerivedClass的使用者而言public_int是protectd,所以無法訪問58     protectedderivedclass.protected_int; //錯誤:成員 BaseClass::protected_int不可訪問59     protectedderivedclass.private_int; //錯誤:成員 BaseClass::private_int不可訪問 60 }

 

C++中public,protected,private的理解