在C++中，子类重载一个操作符时，如何调用父类被重载的操作符函数

使用static_cast运算符将子类转换为父类即可

#include <iostream>

using namespace std;

class Base
{
public:
    Base(int p_n) : n(p_n) { }
    Base& operator=(const Base &base)
    {
        n = base.n;
        return *this;
    }

    friend ostream& operator<<(ostream &os, const Base &base)
    {
        os << "n: " << base.n;
        return os;
    }
private:
    int n;
};

class Sub : public Base
{
public:
    Sub(int p_n, int p_m) : Base(p_n), m(p_m) { }
    Sub& operator=(const Sub &sub)
    {
        Base::operator=(static_cast<Base>(sub) );
        m = sub.m;
        return *this;
    }

    friend ostream& operator<<(ostream &os, const Sub &sub)
    {
        os << static_cast<Base>(sub) << ", ";
        os << "m: " << sub.m;
        return os;
    }
private:
    int m;
};

int main()
{
    Sub sub1(5, 6);
    Sub sub2(-5, -6);

    cout << sub2 << endl;
    sub2 = sub1;
    cout << sub2 << endl;

    return 0;
}

运行结果：

n: -5, m: -6
n: 5, m: 6