87.赋值运算符重载

赋值运算符重载
    系统默认给类提供 赋值运算符写法 是简单值拷贝
    导致如果类中有指向堆区的指针，就可能出现深浅拷贝的问题
    所以要重载 = 运算符
    如果想链式编程 return*this
main.cpp

#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
using namespace std;

//一个类默认创建 默认构造、析构、拷贝构造 operator=赋值运算符 进行简单的值传递
class Person
{
public:

	Person(int a)
	{
		this->m_A = a;
	}


	int m_A;
};

void test01()
{
	Person p1(10);

	Person p2(0);

	p2 = p1; //赋值

	cout << "p2 的m_A===" << p2.m_A << endl;//p2 的m_A===10
}


class Person2
{
public:
	Person2(char * name)
	{
		this->pName = new char[strlen(name) + 1];
		strcpy(this->pName, name);
	}

	//重载 = 赋值运算符
	Person2& operator= (const Person2 & p)
	{
		//判断如果原来已经堆区有内容，先释放
		if (this->pName != NULL)
		{
			delete[] this->pName;
			this->pName = NULL;
		}
		//重新开辟新的空间
		this->pName = new char[strlen(p.pName) + 1];
		strcpy(this->pName, p.pName);

		return *this;
	}

	~Person2()
	{
		if (this->pName != NULL)
		{
			delete[] this->pName;
			this->pName = NULL;
		}
	}

	char * pName;
};

void test02()
{
	Person2 p1("AAAAAAAAA");

	Person2 p2("BBBBBBBBB");

	Person2 p3("");
	p3 = p2 = p1;//会导致重复释放，深拷贝浅拷贝问题，重载“=”解决

	cout << "p2.pName=====" << p2.pName << endl;//p2.pName=====AAAAAAAAA
	cout << "p3.pName====" << p3.pName << endl;//p3.pName====AAAAAAAAA

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

}

int main(){

	//test01();

	test02();

	system("pause");
	return EXIT_SUCCESS;
}