Basic memo: The derived class directly accesses the Private Members of the base class.

A derived class cannot directly access private members of a base class. to access a base class, you must use the base class interface, that is, its member functions. There are two implementation methods:

1. Add protection members to the declaration of the base class, and define private members provided to the base class for access by the derived class as protection members.

2. Declare the member functions of the derived class that need to access the Private Members of the base class as friends.

# Include <iostream> using namespace STD; class base {friend class derived2; // friend int X; protected: // protected int y;}; Class derived1: base // Private inherits {public:/* int getx () {return X; // invalid. Access the private member of the base class} */INT Gety () {return y; // valid, access the protected member of the base class }}; class derived2: Base // Private inheritance {public: int getx () ;}; int derived2: getx () {return X; // you can directly access the private member of the base class} class derived3: public base // public inheritance {pub LIC:/* int getx () {return X; // It cannot be accessed here, because X is a private member of the base and can only be accessed in the base, it cannot be accessed outside.} */INT Gety () {return y ;}}; int main () {int I; derived2 ob; // The constructor with no parameters or the member function initializes X, the constructor assigns a random value to x I = ob. getx (); cout <I <Endl; derived3 ob3; I = ob3.gety (); cout <I <Endl; System ("pause ");}