目录

1.可重载\不可重载运算符

 2.重载运算符：+

3.重载运算符：++

4.重载运算符：- -

5.重载运算符：<< 

6.重载运算符：=

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        运算符重载是一种C++的特性，它允许重新定义或扩展已存在的运算符，以使其适用于用户自定义的数据类型。运算符重载使得您可以创建更直观、自然的操作符行为，从而增强代码的可读性和易用性。

1.可重载\不可重载运算符

 2.重载运算符：+

class Point {
public:
	// 定义属性
	int x;
	int y;
	// 定义构造函数，⽤来初始化属性
	Point() : x(0), y(0) {}
	Point(int x, int y) : x(x), y(y) {}
	// 在类内实现的运算符重载
	Point operator+(const Point& p) const {
		return { x + p.x, y + p.y };
	}
};
// 全局函数实现运算符重载
Point operator-(const Point& p1, const Point& p2) {
	return { p1.x - p2.x, p1.y - p2.y };
}
int main() {
	Point p1(10, 20);
	Point p2(15, 25);
	Point res = p1 + p2; 
	cout << "res.x = " << res.x << ", res.y = " << res.y << endl;//输出 res.x=25,res.y=45
	Point res2 = p1 - p2;
	cout << "res2.x = " << res2.x << ", res2.y = " << res2.y << endl;//输出 res.x=-5,res.y=-5
	return 0;
}

3.重载运算符：++

class Point {
public:
	// 定义属性
	int x;
	int y;
	// 定义构造函数，⽤来初始化属性
	Point() : x(0), y(0) {}
	Point(int x, int y) : x(x), y(y) {}
	// 运算符前置，先运算、后取值
	Point operator++() {
		x++;
		y++;
		return *this;
	}
	// 在类内实现的运算符重载，运算符后置
	Point operator++(int) {
		// 先创建⼀个对象，记录原来的值
		Point tmp = *this;
		// 属性⾃增
		x++;
		y++;
		// 返回之前记录的值
		return tmp;
	}
};
int main() {
	Point p1(10, 20);
	Point p2(15, 25);
	Point res1 = ++p1;
	cout << "res1.x = " << res1.x << ", res1.y = " << res1.y << endl;
	cout << "p1.x = " << p1.x << ", p1.y = " << p1.y << endl;
	Point res2 = p2++;
	cout << "res2.x = " << res2.x << ", res2.y = " << res2.y << endl;
	cout << "p2.x = " << p2.x << ", p2.y = " << p2.y << endl;
	return 0;
}

4.重载运算符：- -

class Point {
public:
	// 定义属性
	int x;
	int y;
	// 定义构造函数，⽤来初始化属性
	Point() : x(0), y(0) {}
	Point(int x, int y) : x(x), y(y) {}
};
//类外实现 运算符前置 先运算再赋值
Point operator--(Point& point) {
	point.x--;
	point.y--;
	return point;
}
//类外实现 运算符后置 先赋值再运算
Point operator--(Point& point, int) {
	Point tmp = point;
	point.x--;
	point.y--;
	return tmp;
}
int main() {
	Point p1(10, 20);
	Point p2(15, 25);
	Point res1 = --p1;
	cout << "res1.x = " << res1.x << ", res1.y = " << res1.y << endl;
	cout << "p1.x = " << p1.x << ", p1.y = " << p1.y << endl;
	Point res2 = p2--;
	cout << "res2.x = " << res2.x << ", res2.y = " << res2.y << endl;
	cout << "p2.x = " << p2.x << ", p2.y = " << p2.y << endl;
	return 0;
}

 

5.重载运算符：<< 

class Point {
	friend ostream& operator<<(ostream& os, const Point& p);
public:
	// 定义属性
	int x;
	int y;
	// 定义构造函数，⽤来初始化属性
	Point() : x(0), y(0), privateField(0) {}
	Point(int x, int y) : x(x), y(y), privateField(0) {}
private:
	int privateField;
};
// 在类外定义运算符重载，全局函数
// 我希望在这⾥能够将Point类中的私有属性也拼接起来，因此需要做成友元
ostream& operator<<(ostream& os, const Point& p) {
	os << "x = " << p.x << ", y = " << p.y << ", privateField = " << p.privateField;
	return os;
}
int main() {
	Point p1(10, 20);
	cout << "p1: " << p1 << endl;
	return 0;
}

6.重载运算符：=

class Person {
public:
	int age;
	int score;
	int* p;
	Person() : age(0), score(0), p(nullptr) {}
	Person(const Person& person) {
		cout << "拷贝构造函数执行了" << endl;
		age = person.age;
		score = person.score;
		p = new int(*person.p);
	}
	// 重载赋值运算符
	Person& operator=(const Person& person) {
		cout << "重载赋值运算符执行了" << endl;
		age = person.age;
		score = person.score;
		p = new int(*person.p);
		return *this;
	}
	~Person() {
		cout << "析构函数执行了" << endl;
		if (p == nullptr) {
			delete p;
			p = nullptr;
		}
	}
};
int main() {
	// 创建⼀个对象
	Person p1;
	p1.age = 18;
	p1.score = 99;
	p1.p = new int(100);
	// 在这⾥，虽然是等号运算符，但是p2对象还没有完成空间开辟、实例化，那么在这⾥会调⽤拷⻉构造函数，⽽⾮重载的等号运算符
	Person p2 = p1;
	// 修改p2的属性值
	p2.age = 20;
	p2.score = 100;
	p2.p = new int(200);
	// 这⾥的p1已经开辟空间了，这⾥就会触发?载的等号运算符
	p1 = p2;
	cout << p1.age << ", " << p1.score << ", " << p1.p << " =>" << *p1.p << endl;
	cout << p2.age << ", " << p2.score << ", " << p2.p << " =>" << *p2.p << endl;
	return 0;
}