c++学习 2.24

1、c++加号运算符重载

1）成员函数重载+号

//本质调用：
Person p3=p1.operator+(p2);

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;
	}

2）全局函数重载+号

//本质调用
Person p3=operator+(p1,p2);

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;
	cout << "temp.m_A " << temp.m_A << " temp.m_B " << temp.m_B << endl;
	return temp;
}

2、c++左移运算符重载

只能利用全局函数重载左移运算符 ,可以配合友元（访问私有属性）输出自定义数据类型

void operator<<(ostream& cout, Person& p)
{
	cout << "p.m_A: " << p.m_A << " p.m_B: " << p.m_B << endl;
}

返回引用，链式编程思想：要在后面追加endl等等，需要继续返回ostream &

ostream & operator<<(ostream& cout, Person& p)
{
	cout << "p.m_A: " << p.m_A << " p.m_B: " << p.m_B << endl;
    return cout;
}

3、递增运算符重载

MyIntefer& operator++()//返回引用，是为了一直对一个数据进行递增
	{
		m_Num++;
		return *this;
	}

如果不加引用，以下输出不同

//myint.m_Num初始化为0；
MyInteger myint;
cout << ++(++myint) << endl;//输出2；
cout << myint << endl;//++运算一次，输出1；

4、赋值运算符重载

#include<iostream>
using namespace std;
class Person
{
public:
	Person(int age)
	{
		m_Age = new int(age);
	}
	Person& operator=(Person& p)//返回引用，链式赋值
	{
		if (m_Age != NULL)
		{
			delete m_Age;
			m_Age = NULL;
		}
		m_Age = new int(*p.m_Age);
		return *this;
	}
	int* m_Age;

};
void test01()
{
	Person p1(18);
	Person p2(20);
	Person p3(30);
	p3 = p2 = p1;
	cout << "p1的年龄为：" << *p1.m_Age << endl;
	cout << "p2的年龄为：" << *p2.m_Age << endl;
	cout << "p3的年龄为：" << *p3.m_Age << endl;
}
int main()
{
	test01();
	int a = 10;
	int b = 20;
	int c = 30;
	c = b = a;
	cout << "a= " << a << endl;
	cout << "b= " << b << endl;
	cout << "a= " << c << endl;
	return 0;
}