目录

P121类和对象-C++运算符重载-加号运算符重载

P122类和对象-C++运算符重载-左移运算符重载

P123类和对象-C++运算符重载-递增运算符重载

P124类和对象-C++运算符重载-赋值运算符重载

P125类和对象-C++运算符重载-关系运算符重载

P126类和对象-C++运算符重载-函数调用运算符重载

运算符重载概念：对已有的运算符重新进行定义，赋予其另一种功能，以适应不同的数据类型

P121类和对象-C++运算符重载-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、成员函数重载+号

示例：

using namespace std; #include<iostream> #include<string> class Person { public: int m_A; int m_B; //1、通过自己写成员函数，实现两个对象相加属性后返回新对象 Person operator+(Person& p) { 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 = 10; p1.m_B = 10; Person p2; p2.m_A = 10; p2.m_B = 10; Person p3 = p1 + p2;//成员函数重载+号本质调用：Person p3=p1.operator+(p2); cout << "p3.m_A = " << p3.m_A << endl; cout << "p3.m_B = " << p3.m_B << endl; } int main() { test01(); system("pause"); return 0; }

结果：

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2、全局函数重载+号

示例：

讯享网using namespace std; #include<iostream> #include<string> class Person { public: int m_A; int m_B; }; Person operator+(Person& a, Person& b) { Person temp; temp.m_A = a.m_A + b.m_A; temp.m_B = a.m_B + b.m_B; return temp; } void test01() { Person p1; p1.m_A = 10; p1.m_B = 10; Person p2; p2.m_A = 10; p2.m_B = 10; Person p3 = p1 + p2;//全局函数重载+号本质调用：Person p3 = operator+(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; }

结果：

3、运算符重载也可以发生函数重载

using namespace std; #include<iostream> #include<string> class Person { public: int m_A; int m_B; //1、通过自己写成员函数，实现两个对象相加属性后返回新对象 /*Person operator+(Person& p) { Person temp; temp.m_A = this->m_A + p.m_A; temp.m_B = this->m_B + p.m_B; return temp; }*/ }; Person operator+(Person& a, Person& b) { Person temp; temp.m_A = a.m_A + b.m_A; temp.m_B = a.m_B + b.m_B; return temp; } //函数重载版本 Person operator+(Person& p1, int num) { 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 = 10; p1.m_B = 10; Person p2; p2.m_A = 10; p2.m_B = 10; Person p3 = p1 + p2;//成员函数重载+号本质调用：Person p3=p1.operator+(p2); //全局函数重载+号本质调用：Person p3 = operator+(p1,p2) cout << "p3.m_A = " << p3.m_A << endl; cout << "p3.m_B = " << p3.m_B << endl; Person p4 = p1 + 20; cout << "p4.m_A = " << p4.m_A << endl; cout << "p4.m_B = " << p4.m_B << endl; } int main() { test01(); system("pause"); return 0; }

结果：

总结1：对于内置的数据类型的表达式的的运算符是不可能改变的

总结2：不要滥用运算符重载

P122类和对象-C++运算符重载-左移运算符重载

作用：可以输出自定义数据类型

讯享网using namespace std; #include<iostream> class Person { public: int m_A; int m_B; //不会利用成员函数重载左移运算符，因为无法实现cout在左侧 }; //只能利用全局函数重载左移运算符 void operator<<(ostream &cout, Person &p) //本质operator<<(cout,p)简化为cout<<p { cout << "m_A = " << p.m_A << " m_B = " << p.m_B << endl; } void test01() { Person p1; p1.m_A = 10; p1.m_B = 10; cout << p1 ; } int main() { test01(); system("pause"); return 0; }

P123类和对象-C++运算符重载-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

示例：

using namespace std; #include<iostream> //自定义整型 class MyInteger { friend ostream& operator<<(ostream& out, MyInteger myint); public: MyInteger() { m_num = 0; } //重载前置++运算符 返回引用是为了一直对一个数据进行递增操作 MyInteger& operator++() { //先++ m_num++; //后返回 return *this; } //重载后置++运算符 //int代表占位参数，可以用于区分前置和后置递增 MyInteger operator++(int) { //先返回 MyInteger temp = *this; //记录当前本身的值，然后让本身的值加1，但是返回的是以前的值，达到先返回后++； m_num++; return temp; } private: int m_num; }; ostream& operator<<(ostream& out, MyInteger myint) { out << myint.m_num; return out; } //前置++ 先++ 再返回 void test01() { MyInteger myInt; cout << ++myInt << endl; cout << myInt << endl; } //后置++ 先返回 再++ void test02() { MyInteger myInt; cout << myInt++ << endl; cout << myInt << endl; } int main() { test02(); system("pause"); return 0; }

P124类和对象-C++运算符重载-赋值运算符重载

c++编译器至少给一个类添加4个函数

1. 默认构造函数(无参，函数体为空)
2. 默认析构函数(无参，函数体为空)
3. 默认拷贝构造函数，对属性进行值拷贝
4. 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，做赋值操作时也会出现深浅拷贝问题

示例：

讯享网class Person { public: Person(int age) { //将年龄数据开辟到堆区 m_Age = new int(age); } //重载赋值运算符 Person& operator=(Person &p) { if (m_Age != NULL) { delete m_Age; m_Age = NULL; } //编译器提供的代码是浅拷贝 //m_Age = p.m_Age; //提供深拷贝 解决浅拷贝的问题 m_Age = new int(*p.m_Age); //返回自身 return *this; } ~Person() { if (m_Age != NULL) { delete m_Age; m_Age = NULL; } } //年龄的指针 int *m_Age; }; void test01() { Person p1(18); Person p2(20); Person p3(30); p3 = p2 = p1; //赋值操作 cout << "p1的年龄为：" << *p1.m_Age << endl; cout << "p2的年龄为：" << *p2.m_Age << endl; cout << "p3的年龄为：" << *p3.m_Age << endl; } int main() { test01(); //int a = 10; //int b = 20; //int c = 30; //c = b = a; //cout << "a = " << a << endl; //cout << "b = " << b << endl; //cout << "c = " << c << endl; system("pause"); return 0; }

P125类和对象-C++运算符重载-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

示例：

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; } else { return false; } } bool operator!=(Person & p) { if (this->m_Name == p.m_Name && this->m_Age == p.m_Age) { return false; } else { return true; } } string m_Name; int m_Age; }; void test01() { //int a = 0; //int b = 0; Person a("孙悟空", 18); Person b("孙悟空", 18); if (a == b) { cout << "a和b相等" << endl; } else { cout << "a和b不相等" << endl; } if (a != b) { cout << "a和b不相等" << endl; } else { cout << "a和b相等" << endl; } } int main() { test01(); system("pause"); return 0; }

P126类和对象-C++运算符重载-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像函数的调用，因此称为仿函数
• 仿函数没有固定写法，非常灵活

示例：

讯享网class MyPrint { public: void operator()(string text) { cout << text << endl; } }; void test01() { //重载的（）操作符 也称为仿函数 MyPrint myFunc; myFunc("hello world"); } class MyAdd { public: int operator()(int v1, int v2) { return v1 + v2; } }; void test02() { MyAdd add; int ret = add(10, 10); cout << "ret = " << ret << endl; //匿名对象调用 cout << "MyAdd()(100,100) = " << MyAdd()(100, 100) << endl; } int main() { test01(); test02(); system("pause"); return 0; }