为什么派生类 Derived_from_Private 是非法的?
我注意到成员函数中有一个对 Base 的引用,但为什么不能有对 Base 类的引用?
class Base {
public:
void pub_mem(); // public member
protected:
int prot_mem; // protected member
private:
char priv_mem; // private member
};
struct Pub_Derv : public Base {
// legal
void memfcn(Base &b) { b = *this; }
};
struct Priv_Derv : private Base {
// legal
void memfcn(Base &b) { b = *this; }
};
struct Prot_Derv : protected Base {
// legal
void memfcn(Base &b) { b = *this; }
};
struct Derived_from_Public : public Pub_Derv {
// legal
void memfcn(Base &b) { b = *this; }
};
struct Derived_from_Private : public Priv_Derv {
// illegal
void memfcn(Base &b) { b = *this; }
};
struct Derived_from_Protected : public Prot_Derv {
// legal
void memfcn(Base &b) { b = *this; }
};