代码中有Building类与GoodGay类,GoodGay类的成员函数作为友元去访问Building类中的private中的成员变量
#include<iostream>
using namespace std;
//为什么此处的Building类与GoodGay类的位置不能颠倒,否则要报错?
class Building;
class GoodGay
{
public:
GoodGay();
void visit();//可以访问Building中私有成员
void visit1();//不可以访问Building中私有成员
Building* builidng;
};
class Building
{
//告诉编译器 GoodGay类中的visit成员函数作为本类的好朋友,可以访问私有函数
friend void GoodGay::visit();
public:
Building();
public:
string m_SittingRoom;
private:
string m_BedRoom;
};
Building::Building()
{
m_SittingRoom = "客厅";
m_BedRoom = "卧室";
}
GoodGay::GoodGay()
{
builidng = new Building;
}
void GoodGay::visit()
{
cout << "visit正在访问" << builidng->m_SittingRoom << endl;
cout << "visit正在访问" << builidng->m_BedRoom << endl;
}
void GoodGay::visit1()
{
cout << "visit1正在访问" << builidng->m_SittingRoom << endl;
}
void test()
{
GoodGay gg;
gg.visit();
gg.visit1();
}
int main(void)
{
test();
system("pause");
return 0;
}
上面的两类中位置互换后:
#include<iostream>
using namespace std;
//为什么此处的Building类与GoodGay类的位置不能颠倒,否则要报错?
class GoodGay;
class Building
{
//告诉编译器 GoodGay类中的visit成员函数作为本类的好朋友,可以访问私有函数
friend void GoodGay::visit();
public:
Building();
public:
string m_SittingRoom;
private:
string m_BedRoom;
};
class GoodGay
{
public:
GoodGay();
void visit();//可以访问Building中私有成员
void visit1();//不可以访问Building中私有成员
Building* builidng;
};
Building::Building()
{
m_SittingRoom = "客厅";
m_BedRoom = "卧室";
}
GoodGay::GoodGay()
{
builidng = new Building;
}
void GoodGay::visit()
{
cout << "visit正在访问" << builidng->m_SittingRoom << endl;
cout << "visit正在访问" << builidng->m_BedRoom << endl;
}
void GoodGay::visit1()
{
cout << "visit1正在访问" << builidng->m_SittingRoom << endl;
}
void test()
{
GoodGay gg;
gg.visit();
gg.visit1();
}
int main(void)
{
test();
system("pause");
return 0;
}