C++运算符重载的详细讲解

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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