运算符重载

1.重载加法运算符

为什么要重载加法运算符？

因为C++提供的加法运算符只能满足基本数据类型间的加法，如果我想让俩个相同的类的对象进行加法的话会报错

所以为了能让俩个相同类的对象进行加法，我们要把这个过程封装到一个函数里面，只不过要多加一个关键字operator而已，让编译器一下子就找到，这个是重载运算符的函数

作用：实现俩个自定义运算符相加

成员函数实现运算符重载

#include <iostream>

using namespace std;

class Box {
	int length;
	int width;
	int height;
public:
	Box() {
		length = 0;
		width = 0;
		height = 0;
	}
	Box(int length,int width,int height) {
		this->length = length;
		this->width = width;
		this->height = height;
	}
	Box(const Box& other) {
		length = other.length;
		width = other.width;
		height = other.height;
	}
	//成员函数重载加法运算符
	Box operator+(const Box& other) {
		Box p;
		p.length = this->length + other.length;
		p.width = this->width + other.width; 
		p.height = this->height + other.height;
		return p;
	}
};
int main() {
	Box a(1,2,3);
	Box b(2, 3, 4);
	Box c = a + b;//直接调用
	Box d;
	d = a.operator+(b);//调用重载运算符的函数
	return 0;
}

全局函数实现运算符的重载

#include <iostream>

using namespace std;

class Box {
	int length;
	int width;
	int height;
	friend Box operator+(const Box& other1, const Box& other2);
	friend Box operator+(const Box& other1, int val);
public:
	Box() {
		length = 0;
		width = 0;
		height = 0;
	}
	Box(int length,int width,int height) {
		this->length = length;
		this->width = width;
		this->height = height;
	}
	Box(const Box& other) {
		length = other.length;
		width = other.width;
		height = other.height;
	}
};
//全局函数重载加法运算符
Box operator+(const Box& other1,const Box& other2) {//不调用成员函数是无法访问私有的成员变量的，需要设置为友元，告诉编译器，我这个重载运算符的函数是你这个类的好朋友，都哥们，能f
	Box p;
	p.length = other1.length + other2.length;
	p.width = other1.width + other2.width;
	p.height = other1.height + other2.height;
	return p;
}
Box operator+(const Box& other1,int val) {
	Box p;
	p.length = other1.length + val;
	p.width = other1.width + val;
	p.height = other1.height + val;
	return p;
}
int main() {
	Box a(1,2,3);
	Box b(2, 3, 4);
	Box c = a + b;
	Box d;
	d=operator+(a,b);
	return 0;
}