Analysis of C ++: youyuan class

Analysis of C ++: youyuan class
I. Reasons for the article

In the previous article, I wrote a friend meta function. This time I wrote a companion article to continue to explore the friend Meta class.

Ii. Definition

All member functions of the youyuan class are the youyuan functions of the other class and can access the hidden information (including private and protected members) in the other class ).

When you want a class to be able to access the private members of another class, you can declare this class as another type of membership class. The statement format for defining a friend Meta class is as follows:

Friend class name;

Among them: friend and class are keywords, and the class name must be a defined class in the program.

Iii. Example

# Include

  
   
Using namespace std; class Radius {friend class Circle; // friend class that declares Circle as Radius: friend void Show_r (Radius & n); // declare Show_r as the friend function public: radius (int x) {r = x ;}~ Radius () {} private: int r ;}; void Show_r (Radius & n) {cout <"circle Radius:" <