C++ 29.类与对象—运算符重载(加号、左移)

运算符重载概念：对已有的运算符重新进行定义，赋予另一种功能，以适应不同的数据类型
总结：
1.对于内置的数据类型的表达式的运算符是不可能改变的
2.不要滥用运算符重载

加号运算符重载

作用：实现两个自定义数据类型相加的运算

#include<iostream>
using namespace std;

class Person
{
public:
	//1.成员函数重载+号。函数名是编译器起的
	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;
	}
	
	int m_A;
	int m_B;

};

//2.全局函数重载+号
//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;
//}

//函数重载
Person operator+(Person &p1, int num)
{
	Person temp;
	temp.m_A = p1.m_A + num;
	temp.m_B = p1.m_B + num;
	return temp;
}
void test01()
{
	Person p1;
	p1.m_A = 10;
	p1.m_B = 10;

	Person p2;
	p2.m_A = 10;
	p2.m_B = 10;
	
	//成员函数重载的本质调用
	//Person p3 = p1.operator+(p2);

	//全局函数重载本质调用
	//Person p3 = operator+(p1，p2);

	Person p3 = p1 + p2;//可简化为这种形式

	//运算符重载，也可以发生函数重载
	Person p4 = p1 + 100;

	cout << "p3.m_A = " << p3.m_A << endl;
	cout << "p3.m_B = " << p3.m_B << endl;

	cout << "p4.m_A = " << p4.m_A << endl;
	cout << "p4.m_B = " << p4.m_B << endl;
}

int main()
{
	test01();

	system("pause");
	return 0;
}

左移运算符重载

作用：可以输出自定义数据类型

#include<iostream>
using namespace std;

//左移运算符重载
class Person
{
	friend ostream & operator<<(ostream &cout, Person 
public:
	//1.成员函数重载  左移运算符 p.operator<<(cout) 简化为p<<cout
	//不会用成员函数调用重载<<运算符，因为无法实现cout在左侧
	//void operator<<(cout){}   
	Person(int a, int b)
	{
		m_A = a;
		m_B = b;
	}
private:
	int m_B;
	int m_A;

};

//2.只能利用全局函数重载左移运算符
//如果想访问私有属性，需要友元
//cout 属于ostream 这个类型
ostream & operator<<(ostream &cout, Person &p)//本质 operator<<(cout,p)//将cout改为out也可以
{
	cout << "m_A = " << p.m_A << "   m_B = " << p.m_B << endl;
	return cout;//不返回不能继续执行其他的cout
}
void test01()
{
	Person p(10,10);
	//p.m_A = 10;
	//p.m_B = 10;

	cout << p << "hello" << endl;
}

int main()
{
	test01();

	system("pause");
	return 0;
}