什么时候必须重载运算符<<？

Question

#include <iostream>

using namespace std;

struct X{
    int _x;
    X(int x=0):_x(x){}
};

int main() {
    X arr[5];
    for (int i = 0;i < 5;i++) {
        arr[i] = i;
    }
    for (int i = 0;i < 5;i++) {
        cout << arr[i] <<",";
    }
    return 0;
}

When must I overload operator << ?

I think since arr has ints so I shouldn't overload << ?

Answer 1

Although your X is just a wrapper around a singular int property it is a different type than int . The good news is you can just delegate to the int method by adding this function:

std::ostream& operator<<(std::ostream& o, const X& x) {
  o << x._x;
  return o;
}