运算符重载注意
- 重载的运算符要易读
- 内置的数据类型的表达式的运算符是不可以改变的
- 不要重载
&&和| |运算符 =，[]和->运算符只能通过成员函数进行重载<<和>>只能通过全局函数配合友元函数进行重载
加号运算符重载
-
如果想让自定义数据类型 进行**+**运算，那么就需要重载 **+**运算符
-
在成员函数 或者 全局函数里 重写 一个**+**运算符的函数
-
函数名operate+(){}
-
运算符重载可以不停重载，接着重载
#include<iostream>using namespace std;class Person{public:Person(){}Person(int a, int b) :m_A(a), m_B(b){}//+号运算符重载 成员函数/*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;};//利用全局函数，进行+号运算符的重载Person operator+(Person &p1, Person &p2) //二元{Person tmp;tmp.m_A = p1.m_A + p2.m_A;tmp.m_B = p1.m_B + p2.m_B;return tmp;}//函数重载 附带运算符再次重载Person operator+(Person &p1, int a) //二元{Person tmp;tmp.m_A = p1.m_A + a;tmp.m_B = p1.m_B + a;return tmp;}void test01(){Person p1(10, 10);Person p2(10, 10);Person p3 = p1 + p2; //p1+p2 从什么表达式转变的？ p1.operator(p2) operator(p1,p2)Person p4 = p1 + 10;//重载的版本cout << "p3的m_A" << p3.m_A << endl << "p3的m_B" << p3.m_B << endl;}int main(){test01();system("pause");return 0;}
左移运算符重载
-
不要随意乱用符号重载
-
内置数据类型的运算符不可以重载
-
cout<< 直接对Person自定义数据类型 进行输出
-
写到全局函数中 ostream& operator<<(ostream & cout,Person & p1){}
-
如果重载时想访问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{friend ostream & operator <<(ostream &cout, Person&p1);public:Person(){}Person(int a, int b){this->m_A = a;this->m_B = b;}/*void operator<<() 重载左移运算符不可以写到成员函数中{}*/private:int m_A;int m_B;};//cout是属于ostream类 //如果向访问私有成员，就要用友元函数ostream & operator <<(ostream &cout, Person&p1) //第一个参数cout 第二个参数p1{cout << "m_A=" << p1.m_A << "m_B=" << p1.m_B;return cout;}void test01(){Person p1(10, 10);cout << p1<<endl;}int main(){test01();system("pause");return 0;}
前置，后置 ++运算符重载
-
自己实现
int类型MyIntege -
内部维护
int数据 -
MyInteger myint -
myint ++ 后置 ++myint前置
-
重载++运算符 operator++()前置 operator++(int )后置
-
前置理念 先++ 后返回自身 后置理念 先保存原有值 内部++ 返回临时数据
#include<iostream>using namespace std;class MyInteger{friend ostream & operator<<(ostream &cout, MyInteger& myInt);public:MyInteger(){m_Num = 0;}//前置++重载//返回引用MyInteger & operator++(){this->m_Num++;return *this;}//用占位参数区分前置和后置//后置++重载//返回值，MyInteger operator++(int){//先保存目前的数据MyInteger tmp = *this;//实际数据++m_Num++;//返回++前的数值return tmp;}//所以前置++好，因为返回引用，少一份开销int m_Num;};ostream & operator<<(ostream &cout, MyInteger& myInt){cout << myInt.m_Num;return cout;}void test01(){MyInteger myInt;//前置++值cout << ++myInt << endl;//后置++值cout << myInt++ << endl;//本身的值cout << myInt << endl;}int main(){test01();system("pause");return 0;}
赋值运算符重载
-
系统默认给类提供 赋值运算符写法 是简单值拷贝
-
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
-
所以要重载=运算符
-
链式编程return *this
#define _CRT_SECURE_NO_WARNINGS#include<iostream>using namespace std;class Person{public:Person(int a){this->m_A = a;}int m_A;};void test01(){Person p1(10);Person p2(0);p2 = p1;cout << "p2的m_A" << p2.m_A << endl;}class Person2{public:Person2(char * name){this->pName = new char[strlen(name) + 1];strcpy(this->pName, name);}//类中重载 =赋值运算符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 test02(){Person2 p1("狗蛋");Person2 p2("狗剩");Person2 p3("");p3=p2 = p1;cout << p2.pName << endl;cout << p3.pName << endl;cout << p2.pName << endl;int a = 10;int b = 20;int c;c = a = b; //都是20cout << a << " " << b << " " << c << endl;}int main(){test02();system("pause");return 0;}
关系运算符重载
#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 false;}return true;}string m_Name;int m_Age;};void test01(){Person p1("小明", 10);Person p2("小强", 15);Person p3("小强", 15);/*int a = 10;int b = 10;if (a == b){cout << "a,b相等" << endl;}*/if (p1 == p2){cout << "p1和p2相等" << endl;}else{cout << "不相等" << endl;}if (p3 == p2){cout << "p3和p2相等" << endl;}else{cout << "不相等" << endl;}if (p1 != p2){cout << "p1和p2不相等" << endl;}else{cout << "相等" << endl;}}int main(){test01();system("pause");return 0;}
函数调用运算符重载
#include<iostream>#include<string>using namespace std;// ()重载class MyPrint{public:void operator()(string text){cout << text << endl;}};void test01(){MyPrint myPrint;myPrint("hello world"); //仿函数}class MyAdd{public:int operator()(int v1,int v2){return v1 + v2;}};void test02(){/*MyAdd myAdd;cout << myAdd(1, 1) << endl;*/cout << MyAdd()(1, 1) << endl; //匿名对象}int main(){//test01();test02();system("pause");return 0;}
)
