【C++】运算符重载

1. 加号运算符重载

#include 
using namespace std;
class Person
{
public:
    // 成员函数实现运算符重载
    // Person operator+(Person &p)
    // {
    //     Person temp;
    //     temp.a = this->a + p.a;
    //     temp.b = this->b + p.b;
    //     return temp;
    // }
    int a;
    int b;
};
// 全局函数实现运算符重载
Person operator+(Person &p1, Person &p2)
{
    Person temp;
    temp.a = p2.a + p1.a;
    temp.b = p2.b + p1.b;
    return temp;
}
int main()
{
    Person p1;
    p1.a = 10;
    p1.b = 20;
    Person p2;
    p2.a = 30;
    p2.b = 40;
    Person p3 = p1 + p2;
    // 成员函数重载本质
    // Person p3 = p1.operator+(p2);
    // 全局函数重载本质
    // Person p3 = operator+(p1, p2);
    cout << p3.a << endl
         << p3.b << endl;
    return 0;
}

2. 左移运算符重载

左移运算符只能利用全局函数重载

#include 
using namespace std;
class Person
{
    friend ostream &operator<<(ostream &cout, Person &p);
public:
    Person(int a, int b)
    {
        this->m_A = a;
        this->m_B = b;
    }
private:
    int m_A;
    int m_B;
};

// 全局函数实现左移运算符重载
ostream& operator<<(ostream& cout, Person& p) {
    cout << "a:" << p.m_A << " b:" << p.m_B;
    return cout;
}
int main()
{
    Person p1(10,20);
    cout << p1 << endl;
    return 0;
}

3. 递增运算符重载

#include 
using namespace std;
class MyInteger
{
    friend ostream &operator<<(ostream &cout, MyInteger myint);

public:
    MyInteger() {
        m_Num = 0;
    }
    // 前置++
    MyInteger& operator++() {
        m_Num++;
        return *this;
    }
    // 后置++
    MyInteger operator++(int) {
        MyInteger temp = *this;
        m_Num++;
        return temp;
    }
private:
    int m_Num;
};
ostream& operator<<(ostream& cout, MyInteger myint) {
    cout << myint.m_Num;
    return cout;
}
// 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()
{
    // test01();
    test02();
    return 0;
}

4. 赋值运算符重载

利用深拷贝解决浅拷贝的问题。

#include 
using namespace std;
class Person
{
public:
    Person(int age)
    {
        m_Age = new int(age);
    }
    Person &operator=(Person &p)
    {
        if (m_Age != NULL)
        {
            delete m_Age;
            m_Age = NULL;
        }
        // 深拷贝
        m_Age = new int(*p.m_Age);
        // 返回自身
        return *this;
    }
    ~Person()
    {
        if (m_Age != NULL)
        {
            delete m_Age;
            m_Age = NULL;
        }
    }
    int *m_Age;
};

int main()
{
    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;
    return 0;
}