1 加号运算符重载
(1)自定义加法数据类型,需要重载+运算符
(2)在成员函数或者全局函数中重写一个+运算符的函数
(3)函数名 operator+() {}
#include<iostream>
using namespace std;
class Person
{
public:
Person() {}
Person(int a,int b):m_A(a),m_B(b)
{}
/*
// 在类中成员函数重载"+"
Person operator+(Person &p)
{
Person tmp;
tmp.m_A = this->m_A + p.m_A;
tmp.m_B = this->m_B + p.m_B;
return tmp;
}
*/
int m_A;
int m_B;
};
// 全局函数中,重载"+"运算符
Person operator+(Person &p1,Person &p2)
{
Person tmp;
tmp.m_A = p1.m_A + p2.m_A;
tmp.m_B = p1.m_B + p2.m_B;
return tmp;
}
void test()
{
Person p1(1,1),p2(2,2);
Person p3;
p3 = p1 + p2;
cout << p3.m_A << " " << p3.m_B << endl;
}
int main()
{
test();
return 0;
}
输出:
3 3
2 左移运算符重载
(1)不要随意乱用符号重载
(2)内置数据类型 的运算符不可以重载
(3)cout << 直接对Person自定义数据类型 进行输出
(4)写到全局函数中ostream& operator << (ostream &cout,Person & p1) {}
(5)如果重载时候想访问p1的私有成员,那么全局函数要做Person的友元函数
#include<iostream>
using namespace std;
class Person
{
public:
Person() {}
Person(int a, int b)
{
this->m_A = a;
this->m_B = b;
}
friend ostream &operator<<(ostream&cout, Person &p1);
// 重载左移运算符不可以写到成员函数中
private:
int m_A;
int m_B;
};
ostream &operator<<(ostream&cout, Person &p1)
{
cout << "p1.m_A=" << p1.m_A << " " << "p1.m_B=" << p1.m_B << endl;
return cout;
}
void test()
{
Person p1(10,10);
cout << p1 << endl;
}
int main()
{
test();
return 0;
}
输出:
p1.m_A=10 p1.m_B=10
3 前置 后置 ++ 运算符重载
(1)myInt++后置 ++ myInt前置
(2)重载++运算符 operator++()前置 operator++(int) 后置
(3)前置理念 先++ 后返回自身 后置理念 先保存住原有值 内部++ 换回临时数据
#include<iostream>
using namespace std;
class MyInteger
{
public:
MyInteger()
{
m_Num = 0;
}
// 前置++重载
MyInteger& operator++()
{
this->m_Num++;
return *this;
}
// 后置++重载
MyInteger operator++(int)
{
MyInteger tmp = *this;
this->m_Num++;
return tmp;
}
friend ostream& operator<< (ostream& out, MyInteger& myInt);
int m_Num;
~MyInteger()
{
cout << "析构函数" << endl;
}
};
ostream& operator<< (ostream& out, MyInteger& myInt)
{
cout << myInt.m_Num;
return out;
}
void test()
{
MyInteger myInt;
cout << ++myInt << endl;
MyInteger p1 = myInt++;
cout << p1 << endl;
// 如果在vs2017开发环境下,下面会报错,但是如果在vs2012开发环境下,则不会。
//cout << myInt++ << endl;
cout << myInt << endl;
}
int main()
{
test();
return 0;
}
输出:
1
析构函数
1
2
析构函数
析构函数
4 智能指针实现
(1)Person类有showAge成员函数
(2)如果new出来的Person对象,需要手动去释放 delete
(3)有了智能指针,让智能指针托管这个Person对象,这样就不用操心了,让智能指针管理
(4)为了让智能指针向普通的Person指针一样使用 就要重载->和
#include <iostream>
using namespace std;
class Person
{
public:
Person(int age)
{
this->m_Age = age;
}
void showAge()
{
cout << "年龄为:" << this->m_Age << endl;
}
~Person()
{
cout << "析构" << endl;
}
int m_Age;
};
// 智能指针
// 用来托管自定义类型的对象,让对象进行自动的释放
class smartPointer
{
public:
smartPointer(Person *person)
{
this->person = person;
}
// 重载->让智能指针对象 向Person *p一样去使用
Person* operator->()
{
return this->person;
}
Person operator*()
{
return *this->person;
}
~smartPointer()
{
cout << "智能指针析构" << endl;
if (this->person != NULL)
{
delete this->person;
this->person = NULL;
}
}
private:
Person *person;
};
void test()
{
// Person p1(10); //开辟在栈上,自动释放
// Person *p1 = new Person(10);// 开辟在堆上,手动释放
// delete p1;
smartPointer sp(new Person(10)); // 开辟到栈上,自动释放
sp->showAge(); // sp->返回的是个指针,应该写成sp->->showAge();单可以这样写,因为编译器给优化了
(*sp).showAge();
}
int main()
{
test();
return EXIT_SUCCESS;
}
输出:
年龄为:10
年龄为:10
析构
智能指针析构
析构
5 赋值运算符重载
(1)系统默认给类提供 赋值运算符写法 是简单值拷贝
(2)导致如果类中有指向堆区的指针,就可能出现深浅拷贝的问题
(3)所以要重载 = 运算符
(4)如果想链式编程 return *this
#include <iostream>
using namespace std;
// 一个类默认创建 默认构造 析构 拷贝构造 opeartor=赋值运算符进行简单的值传递
class Person
{
public:
Person(int a)
{
this->m_A = a;
}
Person(const Person &p)
{
cout << "拷贝" << endl;
this->m_A = p.m_A;
}
int m_A;
};
class Person2
{
public:
Person2(char *name)
{
this->pName = new char[strlen(name)+1];
strcpy(this->pName, name);
}
Person2& operator=(const Person2 &p)
{
// 判断如果原来已经堆区有内容,先释放
if (this->pName != NULL)
{
delete[] this->pName;
this->pName = NULL;
}
this->pName = new char[strlen(p.pName) + 1];
strcpy(this->pName, p.pName);
return *this;
}
~Person2()
{
if (this->pName != NULL)
{
delete[] this->pName;
this->pName = NULL;
}
}
char *pName;
};
void test()
{
Person p1(10);
Person p2(0);
p2 = p1;
cout << "p2的m_A" << p2.m_A << endl;
}
void test02()
{
Person2 p1("赵信");
Person2 p2("无极");
Person2 p3(" ");
p3 = p2 = p1;
cout << p2.pName << endl;
cout << p3.pName << endl;
}
int main()
{
//test();
test02();
return EXIT_SUCCESS;
}
输出:
赵信
赵信
6 关系运算符重载
自定义数据类型 不会内部做比较 == !=,所以要重载
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#include<iostream>
#include<string>
using namespace std;
class Person
{
public:
Person(string name, int age)
{
this->m_Name = name;
this->m_Age = age;
}
bool operator==(Person &p)
{
if (this->m_Name == p.m_Name && this->m_Age == p.m_Age)
{
return true;
}
return false;
}
bool operator!=(Person &p)
{
if (this->m_Name != p.m_Name && this->m_Age != p.m_Age)
return true;
return false;
}
string m_Name;
int m_Age;
};
void test()
{
Person p1("小明",10);
Person p2("小强", 9);
Person p3("小强", 9);
if (p1 == p2)
{
cout << "p1和p2相等" << endl;
}
else
{
cout << "p1、p2不相等" << endl;
}
if (p3 == p2)
{
cout << "p2和p3相等" << endl;
}
else
{
cout << "p2、p3不相等" << endl;
}
if (p1 != p2)
{
cout << "p1、p2不相等" << endl;
}
else
{
cout << "p1和p2相等" << endl;
}
}
int main()
{
test();
return 0;
}
输出:
p1、p2不相等
p2和p3相等
p1、p2不相等
7 函数调用运算符()重载
- ()仿函数 对象() 看似像函数调用-
- MyAdd() 匿名对象
#include<iostream>
#include<string>
using namespace std;
class MyPrint
{
public:
void operator()(string text)
{
cout << text << endl;
}
};
class MyAdd
{
public:
int operator()(int v1, int v2)
{
return v1 + v2;
}
};
void test01()
{
MyPrint myPrint;
myPrint("hello world!"); // 仿函数
}
void test02()
{
MyAdd myAdd;
cout << myAdd(1, 1) << endl;
}
int main()
{
test01();
test02();
return EXIT_SUCCESS;
}
输出:
hello world!
2
8 符号重载总结
- =、[]、()、->操作符只能通过成员函数进行重载
- <<和>>只能通过全局函数和友元函数进行重载
- 不要重载&&和||操作符,因为无法实现短路规则