友元类（18）

#ifndef _A_H_
#define _A_H_
#include <iostream>
using namespace std;

class A {
private:
	int a;
	friend class B;//private  public   protect  权限对友元无影响
public:

};

#endif

#include "A.h"

#ifndef _B_H_
#define _B_H_
#include <iostream>
using namespace std;
class B {
public:
	void show();
};
#endif

#include "B.h"
#include "A.h"
void B::show() {
	A a1;
	a1.a = 1;
	cout << "friend B::show() a1.a = " << a1.a << endl;
}

#ifndef _C_H_
#define _C_H_
#include "A.h"
#include "B.h"

class C {
public:
	void showc();
};
#endif

void C::showc() {

	//A A1;
	//A1.a = 3;非友元不能访问
	cout << "C::showc()" << endl;
}

#include "A.h"
#include "B.h"
#include "C.h"

int main() {
	B B1;
	B1.show();
	return 0;
}