cpp - Friend class－KwCheng's blog

A friend class is a class that can access the private members of a class as though it were a member of that class.

we can define an entire class as a friend as follow :

class X

  int a, b;

 friend class F;

public:

  X() : a(1), b(2) { }

};

class F

public:

 void print(X& x)

 cout << "a is " << x.a << endl;

    cout << "b is " << x.b << endl;

};

int main()

  X xobj;

  F fobj;

  fobj.print(xobj);

  return 0;

We can just define a function of class as friend :

#include <iostream>

using namespace std;

class X;

class Y

public:

  void print(X& x);

};

class X

  int a, b;

 friend void Y::print(X& x);

public:

  X() : a(1), b(2) { }

};

void Y::print(X& x)

 cout << "a is " << x.a << endl;

  cout << "b is " << x.b << endl;

}

int main()

  X xobj;

  Y yobj;

  yobj.print(xobj);

  return 0;

JerryCheng

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