C++ 45 之 赋值运算符的重载

#include <iostream>
#include <string>
#include <cstring>
using namespace std;

class Students05{
public:
    int m_age;
    char* m_name;
    Students05(){

    }
    Students05(const char* name,int age){
        // 申请堆空间保存m_name;
        this->m_name = new char[strlen(name) + 1];
        strcpy(this->m_name, name);
        this->m_age = age;
    }
    // 清空堆空间
    ~Students05(){
        if(this->m_name){
            delete[] this->m_name;
            this->m_name = NULL;
        }
    }
    // 重载赋值运算符 = 
    Students05& operator=(const Students05 &p){
        // 先判断原来的堆区是否有内容
        if(this->m_name){
            delete[] this->m_name;
            this->m_name = NULL;
        }

        this->m_name = new char[strlen(p.m_name) + 1];
        strcpy(this->m_name, p.m_name);
        this->m_age = p.m_age;
        return *this;
    }

    // 拷贝构造函数重载。使用深拷贝解决浅拷贝的free问题
    Students05(const Students05 &p){
        this->m_name = new char[strlen(p.m_name) + 1];
        strcpy(this->m_name, p.m_name);
        this->m_age = p.m_age;
    }
};

int main()
{
    // 编译器默认会给类4个默认函数： 默认构造函数、析构函数、拷贝函数、
    // 拷贝赋值运算符（operator=）
    // stu3 = stu2; // 赋值操作 走拷贝赋值运算符（operator=）
    // Students05 stu3 = stu2; //初始化操作，走复制构造函数 // 此时stu3 刚刚创建
    // Students05 stu3 = Students05(stu2); //初始化操作，走复制构造函数



    // Students05 stu1(18);
    // // Students05 stu2 = stu1; // 相当于Students05 stu2 = Students05(stu1);
    // Students05 stu2;
    // stu2 = stu1;

    // cout << stu1.m_age << endl;


    Students05 stu1("张三",18);
    Students05 stu2("四",28);
    // 执行重载函数时 stu1作为Students05& operator=(const Students05 &p)的参数 里面的this 是stu2
    stu2 = stu1;   // 这种写法叫赋值   // 默认是浅拷贝，执行delete的时候会报错，学要深拷贝才可以


    Students05 stu3("王",39);
    stu3 = stu2 = stu1; // 想链式编程，需要返回当前对象

    Students05 stu4 = stu3; // 隐式法 调用的默认拷贝构造函数，我们自己用new在堆空间中申请的内存，清空的时候会出现错误，需要重载拷贝构造函数
    cout << stu1.m_name << stu1.m_age << endl;
    cout << stu2.m_name << stu2.m_age << endl;
    cout << stu3.m_name << stu3.m_age << endl;

    // int a = 10;
    // int b = 20;
    // int c;
    // c = a = b;
    // cout << "a: " << a << endl;
    // cout << "b: " << b << endl;
    // cout << "c: " << c << endl;

    return 0;
}