如何将+和+=操作符作为非成员函数重载？

#include <iostream>

class MyClass {
private:
    int value;
public:
    MyClass(int val) : value(val) {}

    int getValue() const {
        return value;
    }
};

// 重载+操作符
MyClass operator+(const MyClass& obj1, const MyClass& obj2) {
    int sum = obj1.getValue() + obj2.getValue();
    return MyClass(sum);
}

// 重载+=操作符
MyClass& operator+=(MyClass& obj1, const MyClass& obj2) {
    obj1 = obj1 + obj2;
    return obj1;
}

int main() {
    MyClass obj1(5);
    MyClass obj2(10);

    MyClass obj3 = obj1 + obj2;
    std::cout << "obj3 value: " << obj3.getValue() << std::endl;

    obj1 += obj2;
    std::cout << "obj1 value after += operation: " << obj1.getValue() << std::endl;

    return 0;
}