Friends function, friend class

Friend function

Global functions or other class member functions can be declared as friend functions, and the private functions of the class can be used inside the friend function Member

#includeusing namespace std;class CCar; //Declare the CCar class in advance so that the following CDriver class can use class CDriver{public: void ModifyCar( CCar* pCar); //Modify a car}; class CCar{private: int price; friend int MostExpensiveCar(CCar cars[], int total); //Declare a friend friend void CDriver::ModifyCar(CCar* pCar); / /Declare a friend);void CDriver::ModifyCar(CCar* pCar){ pCar->price += 1000; //value increase after car modification}int MostExpensiveCar(CCar cars[], int total) //seeking the most expensive The price of the car {int tmpMax = -1; for (int i = 0; i tmpMax) tmpMax = cars[i].price; return tmpMax;}int main(){ return 0;}

Friend class

A class A can declare another class B as its friend , All member functions of class B can access the private members of class A objects

Affinity cannot be inherited, only granted to the Class

class CCar{private: int price; friend class CDriver; //declare CDriver as a friend class}; class CDriver{public: CCar myCar; void ModifyCar() //Modify a car {myCar.price += 1000; //Because CDriver is a friend class of CCar, its private members can be accessed here}};int main(){ return 0;}