C++友元

友元

全局函数做友元

---

核心代码

friend void goodGay(Building *building);

完整代码举例

#include<iostream>
using namespace std;
#include<string.h>

class Building
{
    //关键代码
	friend void goodGay(Building *building);
public:
    Building()
	{
	   	m_SittingRoom="客厅";
	   	m_BedRoom="卧室"; 
	} 
public:
	string m_SittingRoom;
private:
	string m_BedRoom;
};

//全局函数
void goodGay(Building *building)
{
	cout<<"好基友正在访问"<<building->m_SittingRoom<<endl;
	cout<<"好基友正在访问"<<building->m_BedRoom<<endl;
	 
} 
int main()
{
	Building b; 
	goodGay(&b);
	
	return 0;
}

类做友元

---

核心代码

friend class GoodGay;

完整代码举例

#include<iostream>
using namespace std;
#include<string.h>

//声明 
class Building;
class GoodGay
{
public:
	GoodGay();
	void visit();//参观函数，访问Building中的属性 
	
	Building *building;
};


class Building
{
	//加上这个就可以表明是他的好朋友 ,然后就可以访问 
	friend class GoodGay;
public:
	
    Building();
	
public:
	string m_SittingRoom;
private:
	string m_BedRoom;
};

//Building构造函数在类外进行初始化 
Building::Building()
{
	this->m_SittingRoom="客厅";
	this->m_BedRoom="卧室"; 
}

//GoodGay构造函数在类外进行初始化 
GoodGay::GoodGay()
{
	building=new Building;
}
//在类外进行访问 
void GoodGay::visit()
{
	cout<<"好基友正在访问"<<building->m_SittingRoom<<endl;
	cout<<"好基友正在访问"<<building->m_BedRoom<<endl;
	 
}

void test()
{
	GoodGay b;
	b.visit();
}
int main()
{
	test();
	return 0;
}

成员函数做友元

---

核心代码

friend void GoodGay::visit();

完整代码举例

#include<iostream>
#include<string.h>
using namespace std;
//成员函数做友元 

class Building;
class GoodGay
{
public:
	GoodGay();
	void visit();//成员函数 可以访问私有 
	void visits();//成员函数  不可以访问私有 
	
	Building *building;
};

class Building
{
	friend void GoodGay::visit();//成员函数做友元 
	//friend class GoodGay;//类做友元 
public:
	Building();
	
public:
	string m_SittingRoom;
private:
	string m_BedRoom;
};
//初始化Building构造函数 类外实现 
Building::Building()
{
	m_SittingRoom="客厅";
	m_BedRoom="卧室";	 
}
//类外实现构造函数 
GoodGay::GoodGay()
{
	building = new Building;
}
void GoodGay::visit()
{
	cout<<"好基友正在访问: "<<building->m_SittingRoom<<endl;
	cout<<"好基友正在访问: "<<building->m_BedRoom<<endl;
}

void GoodGay::visits()
{
	cout<<"好基友正在访问: "<<building->m_SittingRoom<<endl;
	//cout<<"好基友正在访问: "<<building->m_BedRoom<<endl;//这个没有说明，则不可以访问私有 
}

void test01()
{
	GoodGay b;
	b.visit();
	b.visits();
}
int main()
{
	test01();
	return 0; 
} 

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