C++ 《运算符重载》

示例代码

#include "iostream"

//operator+
using namespace std;
class A{
public:
   int m_age;
public:
    A(){}
    A(int age):m_age(age){}
//    A operator+(const A &a){ //成员函数实现重载
//        A temp(0);
//        temp.m_age = m_age+a.m_age;
//        return temp;
//    }
};

A operator+(const A &a,const A &b){ //全局函数实现重载
    A temp(0);
    temp.m_age = a.m_age+b.m_age;
    return temp;
}
A operator+(const A &a,int val){
    A temp(0);
    temp.m_age = a.m_age+val;
    return temp;
}
void test1(){
    A a1(10);
    A a2(20);
    cout<<(a1+a2).m_age<<endl; // 30
    cout<<(a1+44).m_age<<endl; // 54
}

// operator<< 做一运算符重载(成员函数不能实现)
// 一般用于格式化输出
class Person{
public:
    string m_name;
    int m_age;
public:
    Person(string name,int age):m_name(name),m_age(age){}
};
ostream &operator<<( ostream &out,const Person &p){
    out<<"姓名："<<p.m_name<<"年龄："<<p.m_age;
    return out;
}
void test02(){
    Person p("张三",20);
    cout<<p<<endl;
}
// 自增重载
class MyInt{
    friend ostream &operator<<( ostream &out,const MyInt &p);
private:
    int m_Num;
public:
    MyInt(){
        m_Num =0;
    }
    //前置++
    MyInt &operator++(){
        m_Num++;    //先++,再返回
        return *this; //返回对象本身
    }
    //后置++
    MyInt operator++(int ){
        MyInt temp = *this; //记录当前本身的值，然后让本身的值加1，但是返回的是以前的值，达到先返回后++；
        m_Num++;
        return temp;
    }
};
ostream &operator<<( ostream &out,const MyInt &p){
    out<<p.m_Num;
    return out;
}

//赋值运算符重载
class Student{
public:
    int *m_age;
     explicit Student(int age){
        m_age = new int(age);
    }
    Student(const Student &s){ //拷贝函数
        m_age = new int(*s.m_age);
    }
    ~Student(){ //析构函数
        if(m_age != nullptr){
            delete m_age;
            m_age = nullptr;
        }
    }
    //重载赋值运算符
    Student &operator=(const Student &s){
        if(this == &s){
            return *this;
        }
        if(m_age != nullptr){
            delete m_age;
            m_age = nullptr;
        }
        m_age = new int(*s.m_age);
        return *this;
    }
    //重载相等
    bool operator==(Student & stu) const{
         if(*m_age == *stu.m_age){
             return true;
         }else{
             return false;
         }
     }
     //重载不等运算符
     bool operator!=(Student & stu) const{
         if(*m_age != *stu.m_age){
             return true;
         }
         return false;
     }

};

int main(){
    test1();
    return 0;
}