c++编译器至少给一个类添加4个函数
- 默认构造函数(无参,函数体为空)
- 默认析构函数(无参,函数体为空)
- 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,做赋值操作时也会出现深浅拷贝问题
cpp
#include<iostream>
using namespace std;
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)
{
//应该先判断是否属性再堆区,如果有先释放干净,然后再深拷贝
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); //*p.m_Age
//返回自身
return *this; //this =Person operator=
}
~Person()
{
if (m_Age != NULL)
{
delete m_Age;
m_Age = NULL;
}
}
int *m_Age;
};
void test01()
{
Person p1(18);
Person p2(20);
Person p3(30);
p3 = p2 = p1; //赋值
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();
test01();
return 0;
}