1.通过派生类的对象直接访问。前提是public继承

2.通过基类成员函数直接访问基类成员。无论哪种继承方式。基类的public和private都不可以以这种方式访问

3.通过基类名称访问被派生类重定义所隐藏的成员

1 #include
      
        2 using namespace std; 3  4 class Rectangle 5 { 6     public: 7         void setLength(double h) { 8             length = h; 9         }10         void setWidth(double w)11         {12             width = w;13         }14         double getLength()15         {16             return length;17         }18         double getWidth()19         {20             return width;21         }22         double area()23         {24             return width*length;25         }26         double volume()27         {28             return 0;29         }30         void print()31         {32             cout << "\nLength = " << length << "\nWidth = " << width;33         }34     protected:35         double length;36         double width;37 };38 39 class Cube:public Rectangle40 {41     public:42         void setHigh(double h)43         {44             high = h;45         }46         double getHigh()47         {48             return high;49         }50         double area()51         {52             //重定义area函数 53             return 2*(width*length + width*high + high*length);54         }55         double volume()56         {57             return width*length*high;58         }59         60         void print()61         {62             Rectangle::print();63             cout << "\nhigh = " << high << endl;64         }65     private:66         double high;67 };68 69 int main()70 {71     Cube c1;72     c1.setLength(4);73     c1.setHigh(3);74     c1.setWidth(5);75     76     c1.Rectangle::print();77     c1.print();78     cout << "Cube area = " << c1.area() << endl;79     cout << "Cube bottom area = " << c1.Rectangle::area() << endl;80     cout << "Cube volume = " << c1.volume() << endl;81     return 0;82 }