如何在泛型模板的辅助函数中将私有变量作为参数引用

#include <iostream>

template<typename T>
class MyClass {
private:
    T privateVar;

public:
    MyClass(T var) : privateVar(var) {}

    template<typename U>
    friend void helperFunction(MyClass<U>& obj);
};

template<typename U>
void helperFunction(MyClass<U>& obj) {
    std::cout << "Private variable value: " << obj.privateVar << std::endl;
}

int main() {
    MyClass<int> obj(42);
    helperFunction(obj);

    return 0;
}