运算符重载

运算符作用

对已有的运算符重新进行定义，赋予其另一种功能，以适应不容的数据类型

运算符重载需要注意

对于内置的数据类型的表达式的运算符是不可能改变的不要滥用运算符重载

重载’+'运算符

方法

成员函数重载’+' //成员函数实现 + 号运算符重载 Person operator+(const Person& p) { Person temp; temp.m_A = this->m_A + p.m_A; temp.m_B = this->m_B + p.m_B; return temp; } 实现 //成员函数重载本质调用 Person p3 = p1.operator+(p2); //简化调用 Person p3 = p1+p2; 全局函数重载’+' //全局函数实现+号运算符重载 Person operator+(const Person& p1, const Person& p2) { Person temp(0, 0); temp.m_A = p1.m_A + p2.m_A; temp.m_B = p1.m_B + p2.m_B; return temp; } 实现 //全局函数重载本质调用 Person p3 = operator+(p1,p2); //简化调用 Person p3 = p1+p2; 运算符重载也可以发生函数重载 //全局函数实现+号运算符重载 Person operator+(const Person& p2, int val) { Person temp; temp.m_A = p2.m_A + val; temp.m_B = p2.m_B + val; return temp; } 实现 Person p3 = p1 + 100;

<<左移运算符重载

重载<<左移运算符配合友元可以实现输出自定义的数据类型成员函数不可以用来重载左移<<运算符，因为无法实现cout在左侧

示例代码

#include <iostream> #include <string> using namespace std; class Person { friend Person operator + (const Person& p1, const Person& p2); friend ostream & operator << (ostream & cout, const Person& p); public: Person() {} Person(string name,int age,int tech) { this->m_Name = name; this->m_Age = age; this->m_Techology = tech; } void Print() { cout << "Name:" << this->m_Name << endl; cout << "Age:" << this->m_Age << endl; cout << "Techology:" << this->m_Techology << endl; } private: string m_Name; int m_Age; int m_Techology; }; Person operator + (const Person& p1, const Person& p2) { Person tmp; tmp.m_Name = "baby"; tmp.m_Age = p1.m_Age + p2.m_Age; tmp.m_Techology = p1.m_Techology + p2.m_Techology; return tmp; } ostream & operator << (ostream& cout, const Person &p) { cout << "Name:" << p.m_Name << endl; cout << "Age:" << p.m_Age << endl; cout << "Techology:" << p.m_Techology << endl; return cout; } int main() { Person p1("ZXW", 18, 100); Person p2 = Person("HHK",21,100); Person p3 = p1 + p2; p1.Print(); p2.Print(); p3.Print(); cout << endl; cout << p1 << p2 << p3; return 0; }

输出

Name:ZXW Age:18 Techology:100 Name:HHK Age:21 Techology:100 Name:baby Age:39 Techology:200 Name:ZXW Age:18 Techology:100 Name:HHK Age:21 Techology:100 Name:baby Age:39 Techology:200

++递增运算符重载

作用：通过重载递增运算符，实现自己的整形数据

重载前置++运算符

//前置++递增运算符 Myint& operator++() { this->m_Value++; return *this; } 返回的一定是引用，因为++(++x)可以叠加，体现了链式编程思想

重载后置++运算符

//后置++递增运算符 Myint operator++(int) { Myint tmp = *this; this->m_Value++; return tmp; } 返回的一定是值，因为(x++)++语法是错误的，没有采用链式编程思想

示例代码

#include <iostream> using namespace std; class Myint { friend ostream& operator<<(ostream& out, const Myint& myint); public: Myint() {} Myint(int x) { this->m_Value = x; } //前置++递增运算符 Myint& operator++() { this->m_Value++; return *this; } //后置++递增运算符 Myint operator++(int) { Myint tmp = *this; this->m_Value++; return tmp; } private: int m_Value; }; ostream& operator<<(ostream& out, const Myint& myint) { cout << myint.m_Value << endl; return cout; } int main() { Myint myint1(10); cout << ++(++myint1) << endl; cout << myint1++ << endl; cout << myint1 << endl; return 0; }

输出

12 12 13

=运算符重载

C++编译器至少给一个类添加4个函数

默认构造函数（无参，函数体为空）默认析构函数（无参，函数体为空）默认拷贝构造函数，对属性值进行值拷贝赋值运算符operator=，属性进行值拷贝（编译器提供的是浅拷贝） 如果类中有属性指向堆区，做赋值操作时也会出现深浅拷贝问题 （浅拷贝会引发堆区内存重复释放，程序进而崩溃，需要用深拷贝来解决）

关系运算符重载

作用：重载关系运算符，可以让两个自定义类型对你选哪个进行对比操作

bool operator==(const Person& p) { if (this->m_Name == p.m_Name && this->m_Age == p.m_Age) return true; else return false; }

函数调用运算符

函数调用运算符重载后的使用方式非常像函数的调用，所以称为仿函数仿函数没有固定的写法，非常灵活STL库中用到了大量的仿函数

示例程序

class{ int operator()(int x,int y){ return x+y; } } main(){ 类名 add; cout<<add(100,100)<<endl; }

输出

200

匿名函数对象

cout<<add()(100,100)<<endl; add()是一个匿名对象 add()(100,100)是一个匿名函数对象

输出

200