C++中一共有两种自增运算符
1、前置自增运算符
2、后置自增运算符

前置自增运算符可以链式使用，而后置自增运算符不可以链式使用

1、重载前置运算符

by 成员函数的方式

#include <iostream>
using namespace std;
class Student{
public:
    int m_age;
    double m_score;
    Student(){
        m_age = 19;
        m_score = 100.0;
    }
    Student(const Student& stu){
        m_age = stu.m_age;
        m_score = stu.m_score;
    }
    Student& operator++(){  // 这里一定要是返回对象的引用  否则链式使用的时候会出问题
         (this->m_age)++;
         (this->m_score)++;
         return *this;
    }
};
ostream& operator<<(ostream& os,const Student& stu){  
    os << "m_age = " << stu.m_age << endl;
    os << "m_soce = " << stu.m_score << endl;
    return os;
}
istream& operator>>(istream& is,Student& stu){
    cout << "m_age: ";
    is >> stu.m_age;
    cout << "m_score: ";
    is >> stu.m_score;
    return is;
}
void test1(){
    Student stu;
    cin >> stu;
    cout << stu;
    cout << ++stu << endl;
    cout << ++(++stu) << endl;  // 可以像这个样子链式使用前置自增
    return;
}
int main(){
    test1();
    system("pause");
    return 0;
}

虽然链式使用了两次自增运算符，但是实际上数据只自增了一次。
原因： 第二次自增的时候，系统重新构造出了一个数据相同的对象。因此，重载前置运算符的时候的返回值一定是对象的引用。

2、重载后置运算符

by 成员函数

#include <iostream>
using namespace std;
class Student{
public:
    int m_age;
    double m_score;
    Student(){
        m_age = 19;
        m_score = 100.0;
    }
    Student(const Student& stu){
        m_age = stu.m_age;
        m_score = stu.m_score;
    }
    Student& operator++(){
         (this->m_age)++;
         (this->m_score)++;
         return *this;
    }
    Student operator++(int){
        Student tempStudent(*this); 
        m_age ++;
        m_score ++;
        return tempStudent;
    }
};
ostream& operator<<(ostream& os,const Student& stu){  //重载左移运算符
    os << "m_age = " << stu.m_age << endl;
    os << "m_soce = " << stu.m_score << endl;
    return os;
}
istream& operator>>(istream& is,Student& stu){ // 重载右移运算符
    cout << "m_age: ";
    is >> stu.m_age;
    cout << "m_score: ";
    is >> stu.m_score;
    return is;
}
void test1(){
    //Student stu = *(new Student());  该方法可以将数据开辟到堆区
    Student stu;  // 默认构造函数创建对象
    cout << stu << endl;
    cout << (stu++) << endl;
    //cout << (stu++)++ << endl;  // 是不允许这样的操作的。
    cout << stu << endl;
    return;
}
int main(){
    test1();
    system("pause");
    return 0;
}