大虾指点下，关于基类，派生类和继承的，C++ PRIMER的疑问

[boxiaoliao]

正在看，有个地方表示不懂
class Base {
public:
void basemem(); // public member
protected:
int i; // protected member
// ...
};
struct Public_derived : public Base {
int use_base() { return i; } // ok: derived classes can access i
// ...
};
struct Private_derived : private Base {
int use_base() { return i; } // ok: derived classes can access i
};


struct Derived_from Private : public Private_derived {
// error: Base::i is private in Private_derived
int use_base() { return i; }
};
struct Derived_from_Public : public Public_derived {
// ok: Base::i remains protected in Public_derived
int use_base() { return i; }
};


为啥Derived_from Private的成员函数use_base返回i是错误的？
按我的理解，i也是Derived_from Private的一个private成员，成员函数使用私有成员有什么不对？

[boxiaoliao]

引用 2 楼 zmlovelx 的回复:

private继承时，只有基类的public与protected的成员成为派生类的private成员。

重新看了一遍，明白了 但实际上基类的private成员在派生类中还是存在的，只是无法访问？

[zcdabing]

class Base { public: void basemem(); // public member protected: int i; // protected member // ... }; struct Public_derived : public Base { int use_base() { return i; } // ok: derived classes can access i // ... }; struct Private_derived : private Base { int use_base() { return i; } // ok: derived classes can access i }; struct Derived_from Private : public Private_derived { // error: Base::i is private in Private_derived int use_base() { return i; }//private i 你访问不了 }; struct Derived_from_Public : public Public_derived { // ok: Base::i remains protected in Public_derived int use_base() { return i; } };

[帅得不敢出门]

private继承时，只有基类的public与protected的成员成为派生类的private成员。