C++ 运算符重载<<

#include <iostream>
using namespace std;

class Good
{
public:
    int member;
    Good(int a): member(a)
    {
        cout << "调用构造" << endl;
    }
    void show()
    {
        cout << member << endl;
    }
    Good operator+(const Good& obj)
    {
        return Good(member - obj.member);
    }
    
    friend ostream& operator<<(ostream& os, Good& obj)
    {
        os << obj.member << "运算符重载" << endl;
        
        return os; //这句话关键，便于重复调用 
    }
};

int main(int argc, char *argv[])
{
    Good a(10), b(20);
    Good c = a + b;
    cout << c;
    c.show();
    return 0;
}