复习 --- C++运算符重载

.5 运算符重载

运算符重载概念：对已有的运算符重新进行定义，赋予其另外一种功能，以适应不同的数据类型

4.5.1 加号运算符重载

作用：实现两个自定义数据类型相加的运算

 1  #include<iostream>2  using namespace std;3  //加号运算符重载4  class Person5  {6      public:7          //成员函数重载+号8          Person operator+(Person &p)9          {10              Person temp;11              temp.m_A = p.m_A + this->m_A;12              temp.m_B = p.m_B + this->m_B;13              return temp;14          }15          int m_A;16          int m_B;17  };18  19  //全局函数重载20  Person operator+(Person &p1,Person &p2)21  {22      Person temp;23      temp.m_A = p1.m_A + p2.m_A;24      temp.m_B = p1.m_B + p2.m_B;25      return temp;26  }27  void test01()28  {29      Person p1;30      p1.m_A = 10;31      p1.m_B = 10;32      Person p2;33      p2.m_A = 10;34      p2.m_B = 10;35  36      Person p3 = p1 + p2;37      //成员函数重载的本质38      Person p3 = p1.operator+(p2);39      //全局函数重载的本质40      Person p5 = operator+(p1,p2);41      cout << p3.m_A << " " << p3.m_B<<endl;42  }43  //1.成员函数重载+号44  int main(int argc, const char *argv[])45  {46      test01();47      return 0;48  }

4.5.2 左移运算符重载

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 1  #include<iostream>2  using namespace std;3  4  //左移5  class Person6  {7      public:8          //内置重载函数 左移运算符9          //实现不了10          int m_A;11          int m_B;12  };13  14  //全局重载函数15  void operator<<(ostream &cout ,Person &p)16  {17      cout << "m_A = " << p.m_A << "m_B = " <<p.m_B << endl;18  }19  20  void test01()21  {22      Person p;23      p.m_A = 10;24      p.m_B = 10;25  26      cout << p.m_A <<endl;27  }28  int main(int argc, const char *argv[])29  {30      test01();31      return 0;32  }

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4.5.3递增运算符重载

作用：通过重载递增运算符，实现自己的整型数据

 #include<iostream>using namespace std;​class Myinterger{friend ostream & operator<<(ostream &cout,Myinterger myint);public://重载前置++函数//返回引用是为了一直对一个数据进行递增操作Myinterger& operator++(){m_Num++;return *this;}​//重载后置++函数//int 是占位参数Myinterger operator++(int){//先记录当时结果Myinterger temp = *this;m_Num++;return temp;}Myinterger(){m_Num = 0;}private:int m_Num;};//重载<<运算符ostream& operator<<(ostream &cout,Myinterger myint){cout << myint.m_Num;return cout;}​void test01(){Myinterger myint;++myint;cout << myint << endl;}​int main(int argc, const char *argv[]){test01();return 0;}

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4.5.4 赋值运算符重载

1.编译器至少给一个类添加4个函数

• 默认构造函数（无参，函数为空）

• 默认析构函数（无参，函数为空）

• 默认拷贝构造函数，对属性进行值拷贝

• 赋值运算符 operator=,对属性进行值拷贝

如果类中有属性指向堆区，做赋值操作时会出现深浅拷贝问题

 #include<iostream>using namespace std;​class Person{public://等号重载函数Person& operator=(Person &p){//实现浅拷贝//先判断是否有属性在堆区，先释放在深拷贝if (m_age != NULL){delete m_age;m_age = NULL;}m_age = new int(*p.m_age);return *this;}Person(int age){m_age = new int(age);}​int *m_age;​~Person(){if (m_age != NULL){delete m_age;}}};​​void test01(){Person p1(18);Person p2(12);p2 = p1;cout << "p1的年龄为："<<*p1.m_age<<endl;cout << "p1的年龄为："<<*p2.m_age<<endl;}​int main(int argc, const char *argv[]){test01();return 0;}​

4.5.5 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象进行对比操作

 #include<iostream>#include<string>using namespace std;class Person{public://重载==bool operator==(Person &p){if (m_name == p.m_name && m_age == p.m_age){return true;}return false;}Person(string name , int age){m_name = name;m_age = age;}private:string m_name;int m_age;};​void test01(){Person p1("zyl",18);Person p2("zyl",18);bool b = (p1==p2);cout << b  << endl;​}​int main(int argc, const char *argv[]){test01();return 0;}

4.5.6 函数调用运算符重载

• 函数调用运算符()也可以重载

• 由于重载后使用的方式非常想函数的调用，因此也成为仿函数

• 仿函数你没有固定写法，非常灵活

 #include<iostream>#include<string>using namespace std;​class MyPrint{public:void operator()(string text){cout << text <<endl;}};​void test01(){MyPrint mp;mp("hello");//仿函数}​int main(int argc, const char *argv[]){test01();return 0;}​