[C++知识库]友元/运算符重载

友元（friend）

全局函数/类/成员函数都可以作友元

全局函数作友元 从而访问私有成员

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

class fz
{
	friend void hpy(fz* fz);//将hpy函数设置为fz类的友元

public:
	fz()
	{
		m_kt = "客厅";
		m_ws = "卧室";
	}
public:
	string m_kt;
private:
	string m_ws;
};
void hpy(fz *fz)
{
	cout << fz->m_kt << endl;
	cout << fz->m_ws << endl;//友元函数可以访问类内私有成员
}
int main()
{
	fz fz1;
	hpy(&fz1);
	return 0;
}

类作为友元 访问 其他类内私有成员

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

class Building
{
	friend class goodGay;
public:
	string m_kt;
public:
	Building();
private:
	string m_ws;
};
Building::Building()
{
	m_kt = "客厅";
	m_ws = "卧室";
}

class goodGay
{
public:
	goodGay();
	void visit();
	Building* bd;
private:

};
void goodGay::visit()
{
	cout << bd->m_kt << endl;
	cout << bd->m_ws << endl;
}
goodGay::goodGay()
{
	bd = new Building;
}

int main() 
{
	goodGay gg;
	gg.visit();
	return 0;
}

成员函数作友元

#include <iostream>
#include <string>
using namespace std;
class building
{
	//friend class goodGay;
	friend void goodGay::visit();
public:
	building();
	~building();
	string m_kt;

private:
	string m_ws;
};
building::building()
{
	m_kt = "客厅";
	m_ws = "卧室";
}
building::~building()
{
}

class goodGay
{
public:
	goodGay();
	void visit();
	void visit2();
	building* bd;

	~goodGay();
private:

};
goodGay::goodGay()
{
	bd = new building;
}
goodGay::~goodGay()
{
}
void goodGay::visit()
{
	cout << bd->m_kt << endl;
	cout << bd->m_ws << endl;
}
void goodGay::visit2()
{
	cout << bd->m_kt << endl;
}
int main()
{
	goodGay* g1 = new goodGay;
	g1->visit();
	g1->visit2();
	return 0;
}

加号运算符重载（operator+ ）可以发生重载

#include <iostream>
#include <string>
using namespace std;
class person
{
public:
	person();
	~person();
	//person operator+(person &p);
	int m_a;
	int m_b;

private:

};
person::person()
{
}

person::~person()
{
}
/*person person::operator+(person& p)
{
	person temp;
	temp.m_a = this->m_a + p.m_a;
	temp.m_b = this->m_b + p.m_b;
	return temp;
}
*/
/**/person operator+(person& p1, person& p2)
{
	person temp;
	temp.m_a = p1.m_a + p2.m_a;
	temp.m_b = p1.m_b + p2.m_b;
	return temp;
}
void test01()
{
	person p1;
	p1.m_a = 10;
	p1.m_b = 10;
	person p2;
	p2.m_a = 11;
	p2.m_b = 12;
	//p3 = p1.operator+(p2);//成员函数本质调法
	//p3 = operator+(p1,p2);//全局函数本质调法
	person p3 = p1 + p2;

	cout << p3.m_a << endl;
	cout << p3.m_b << endl;

}
int main()
{
	test01();
	return 0;
}