Cpp-learning/运算符重载2/4、赋值运算符重载.cpp

//4.5.4   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

#if(0)

#include <iostream>

class Person
{
public:
	Person(int age)
	{
		m_Age = new int(age);

	}

	~Person()
	{
		if (m_Age != NULL)
		{
			delete m_Age;
			m_Age = NULL;
		}
	}

	//重载  赋值运算符

	Person& operator=(Person &p)
	{
		//编译器是提供的浅拷贝

		//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，再深拷贝
		if (m_Age != NULL)
		{
			delete m_Age;
			m_Age = NULL;
		}

		//深拷贝
		m_Age = new int(*p.m_Age);

		return *this;

	}



	int* m_Age;

};

void test01()
{
	Person p1(18);

	Person p2(20);

	Person p3(30);

	p3 = p2 = p1;                    //赋值运算操作

	std::cout << "p1的年龄为：" << *p1.m_Age << std::endl;
	std::cout << "p2的年龄为：" << *p2.m_Age << std::endl;
	std::cout << "p3的年龄为：" << *p3.m_Age << std::endl;
}

int main()
{
	test01();

	//int a = 10;

	//int b = 20;

	//int c = 30;

	//c = b = a;

	//std::cout << "a = " << a << std::endl;
	//std::cout << "b = " << b << std::endl;
	//std::cout << "c = " << c << std::endl;

	system("pause");

	return 0;
}

#endif