赋值运算符重载

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拷贝问题

代码示例：

#include <iostream>
using namespace std;
//赋值运算符重载
class Person
{
   
public:
       Person(int age)
       {
   
              m_Age = new int(age);
       }
       ~Person()
       {
   
              if (m_Age != NULL)
              {
   
                     delete m_Age;
                     m_Age = NULL;
              }
       }
       //重载 赋值运算
       Person& operator=(Person &p)
       {
   
              //编译器是提供浅拷贝
              //m_Age = p.m_Age;
              //应该先判断是否有属性在堆区，如果有先释放干净，然后在深拷贝
              if (m_Age != NULL)
              {
   
                     delete m_Age;
                     m_Age = NULL;
              }
              //深拷贝
              m_Age = new int(*p.m_Age);
              //返回对象本身
              return *this;
       }
       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;
       return 0;
}

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