在 C++ 中如何用最少的代码实现访问所有子类中的某种变量？

class Base {
public:
    virtual ~Base() {}
    virtual int getValue() const = 0;
};

class Derived1 : public Base {
public:
    int getValue() const override {
        return value1;
    }
private:
    int value1 = 1;
};

class Derived2 : public Base {
public:
    int getValue() const override {
        return value2;
    }
private:
    int value2 = 2;
};

int main() {
    Derived1 d1;
    Derived2 d2;
    Base& b1 = d1;
    Base& b2 = d2;
    std::cout << b1.getValue()<< std::endl; // 输出 1
    std::cout << b2.getValue()<< std::endl; // 输出 2
    return 0;
}