加号运算符重载

对于内置数据类型，编译器知道如何运算

但是对于自己封装的类，编译器无法进行运算

这时可以通过自己定义运算符重载进行运算

operator+

通过成员函数重载+号

#include<iostream>using namespace std;class Person{public: int m_a; int m_b; //通过成员函数实现重载 Person operator+ (Person &p) { //创建一个临时变量 Person temp; temp.m_a = this->m_a + p.m_a; temp.m_b = this->m_b + p.m_b; return temp; }};void test01(){ Person p1; p1.m_a = 66; p1.m_b = 44; Person p2; p2.m_a = 6; p2.m_b = 4; Person p3; //通过函数原型调用 p3 = p1.operator+(p2); //简便调用 //p3 = p1 + p2; cout << "p3.m_a:" << p3.m_a << endl; cout << "p3.m_b:" << p3.m_b << endl;}int main(){ test01(); system("pause"); return 0;}

注意两种调用方式

通过函数原型调用

p3 = p1.operator+(p2);

简便调用

p3 = p1 + p2;

通过全局函数重载+号

#include<iostream>using namespace std;class Person{public: int m_a; int m_b;};//通过全局函数实现重载Person operator+ (Person& p1, Person& p2){ //创建一个临时变量 Person temp; temp.m_a = p1.m_a + p2.m_a; temp.m_b = p1.m_b + p2.m_b; return temp;}void test01(){ Person p1; p1.m_a = 66; p1.m_b = 44; Person p2; p2.m_a = 6; p2.m_b = 4; Person p3; //函数原型调用 p3 = operator+(p1,p2); //简便调用 //p3 = p1 + p2; cout << "p3.m_a:" << p3.m_a << endl; cout << "p3.m_b:" << p3.m_b << endl;}int main(){ test01(); system("pause"); return 0;}

注意两种调用方式

通过函数原型调用

p3 = operator+(p1,p2);

简便调用

p3 = p1 + p2;

运算符重载发生函数重载

运算符重载可以发生函数重载：Person+int等等

#include<iostream>using namespace std;class Person{public: int m_a; int m_b;};//通过全局函数实现重载Person operator+ (Person& p1, int num){ //创建一个临时变量 Person temp; temp.m_a = p1.m_a + num; temp.m_b = p1.m_b + num; return temp;}void test01(){ Person p1; p1.m_a = 66; p1.m_b = 44; Person p2; p2.m_a = 6; p2.m_b = 4; Person p3; //函数原型调用 //p3 = operator+(p1,55); //简便调用 p3 = p1 + 55; cout << "p3.m_a:" << p3.m_a << endl; cout << "p3.m_b:" << p3.m_b << endl;}int main(){ test01(); system("pause"); return 0;}

调用方法和定义方法与上面相同，不再多余赘述

总结

1、系统内置数据类型的表达式不可改变

2、不要滥用运算符重载

左移运算符

不利用成员函数重载左移运算符

没有具体演示，因为报错，我也没写出来

下面通过全局函数实现

#include<iostream>using namespace std;class Person{public: int m_a; int m_b; };ostream& operator<<(ostream& cout,Person&p){ cout << "p.m_a=" <<p. m_a << " p.m_b=" <<p. m_b << endl; return cout;}void test01(){ Person p1; p1.m_a = 44; p1.m_b = 66; cout << p1 << endl;}int main(){ test01(); system("pause"); return 0;}

因为要实现链式，实现追加，所以返回值必须是ostream

总结

配合友元实现自定义输出类型

递增运算符重载

递增运算符重载

#include<iostream>using namespace std;class myInt{ friend ostream& operator<<(ostream& cout, myInt num);public: myInt() { this->m_a = 0; } //前置++运算符重载 myInt& operator++()//返回引用是为了一直对一个数据进行递增，否则函数默认返回一个新的数 { //先进行++ m_a++; //然后返回自身 return *this; } //后置++运算符重载 myInt operator++(int)//int表示占位参数，用于区分前置后置参数 { //先记录当前的值 myInt temp=*this; //再递增 m_a++; //然后返回记录的值 return temp; }private: int m_a; };//左移运算符重载ostream& operator<<(ostream& cout, myInt num){ cout << num.m_a; return cout;}void test01(){ myInt myint; cout << myint << endl; cout << ++myint << endl; cout << myint << endl;}int main(){ test01(); system("pause"); return 0;}

赋值运算符重载

#include<iostream>using namespace std;class Person{public: Person(int num)//将数据开辟到堆区 { m_a = new int(num); } ~Person() { if (m_a != NULL) { delete m_a; m_a = NULL; } } //重载赋值运算符 Person& operator=(Person &p)//返回值用Person返回本身，可执行连等 { //先判断是否有属性在堆区，如果有先释放干净 if (m_a != NULL) { delete m_a; m_a = NULL; } m_a = new int(*p.m_a); return *this; } int* m_a; };void test01(){ Person p1(18); Person p2(209); Person p3(9); p2 = p1 = p3; cout << *p1.m_a << endl; cout << *p2.m_a << endl; cout << *p3.m_a << endl;}int main(){ test01(); system("pause"); return 0;}

关系运算符重载

#include<iostream>using namespace std;#include<string>class Person{public: Person(string name, int age) { this->age = age; this->name = name; } bool operator==(Person& p) { if (this->age == p.age && this->name == p.name) { return true; } else { return false; } } bool operator!=(Person& p) { if (this->age == p.age && this->name == p.name) { return false; } else { return true; } } string name; int age; };void test01(){ Person p1("gouride", 19); Person p2("gouride", 19); if (p1 == p2) { cout << "p1和p2相同" << endl; } else { cout << "p1和p2不相同" << endl; } if (p1 != p2) { cout << "p1和p2不相同" << endl; } else { cout << "p1和p2相同" << endl; }}int main(){ test01(); system("pause"); return 0;}

函数调用重载

仿函数

#include<iostream>using namespace std;#include<string>class Myprint{public: void operator()(string name) { cout << name << endl; } int operator()(int a,int b) { return a + b; }};void test01(){ Myprint myprint; myprint("测试"); //匿名对象调用 cout << Myprint()(4,6) << endl;}int main(){ test01(); system("pause"); return 0;}

总结

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