成员函数做友元

代码示例：
#include <iostream>
using namespace std;
#include <string>
class Building;
class GoodGay
{
   
public:
       GoodGay();
       void visit();        //让visit函数可以访问Building中私有成员
       void visit2();             //让visit2函数不可以访问Building中私有成员
       Building *building;
};
class Building
{
   
       //告诉编译器 GoodGay类下的visit成员函数作为本类的好朋友，可以访问私有成员
       friend void GoodGay::visit();
public:
       Building();
public:
       string m_SittingRoom;      //客厅
private:
       string m_BedRoom;          //卧室
};
Building::Building()
{
   
       m_SittingRoom = "客厅";
       m_BedRoom = "卧室";
}
GoodGay::GoodGay()
{
   
       building = new Building;
}
void GoodGay::visit()
{
   
       cout << "visit 函数正在访问：" << building->m_SittingRoom << endl;
       cout << "visit 函数正在访问：" << building->m_BedRoom << endl;
}
void GoodGay::visit2()
{
   
       cout << "visit2 函数正在访问：" << building->m_SittingRoom << endl;
       //cout << "visit 函数正在访问：" << building->m_BedRoom << endl;
}
void test01()
{
   
       GoodGay gg;
       gg.visit();
       gg.visit2();
}
int main()
{
   
       test01();
       return 0;
}

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