左移运算符重载

作用：可以输出自定义数据类型

class Person {
    friend ostream& operator<<(ostream& out, Person& p);

public:

    Person(int a, int b)
    {
        this->m_A = a;
        this->m_B = b;
    }

    //成员函数 实现不了  p << cout 不是我们想要的效果
    //void operator<<(Person& p){
    //}

private:
    int m_A;
    int m_B;
};

//全局函数实现左移重载
//ostream对象只能有一个
ostream& operator<<(ostream& out, Person& p) {
    out << "a:" << p.m_A << " b:" << p.m_B;
    return out;
}

void test() {

    Person p1(10, 20);

    cout << p1 << "hello world" << endl; //链式编程
}

int main() {

    test();

    system("pause");

    return 0;
}

总结：重载左移运算符配合友元可以实现输出自定义数据类型