38. 赋值运算符和[]运算符重载

• 赋值运算符重载

• 编译器会默认个一个类添加4个函数

• 默认构造、析构 、 拷贝构造（值拷贝） 、 operator=（值拷贝）

• 如果类中有属性创建在堆区，利用编译器提供的 = 赋值运算就会出现 堆区内存重复释放的问题
• 解决方案：利用深拷贝 重载 =运算符
• Person& operator=( const Person &p)

• []运算符重载

• int& operator[](int index);
• 实现访问数组时候利用[] 访问元素

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

//编译器 默认给一个类4个函数   默认构造   析构   拷贝构造 （值拷贝）  operator= (值拷贝)
class Person
{
public:
	Person(char * name, int age)
	{
		this->m_Name = new char[strlen(name) + 1];
		strcpy(this->m_Name, name);
		this->m_Age = age;
	}

	//重载 =
	Person& operator=( const Person &p)
	{
		//先判断原来堆区释放有内容，如果有先释放
		if (this->m_Name != NULL)
		{
			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
	Person(const Person & p)
	{
		this->m_Name = new char[strlen(p.m_Name) + 1];
		strcpy(this->m_Name, p.m_Name);
		this->m_Age = p.m_Age;
	}

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

	char * m_Name;
	int m_Age;
};


void test01()
{
	Person p1("Tom",10);
	
	Person p2("Jerry",19);
	p2 = p1;

	Person p3("", 0);
	p3 = p2 = p1;


	Person p4 = p3;

	cout << "p1姓名： "<< p1.m_Name << "  p1年龄： " << p1.m_Age << endl;
	cout << "p2姓名： "<< p2.m_Name << "  p2年龄： " << p2.m_Age << endl;
	cout << "p3姓名： " << p3.m_Name << " p3年龄： " << p3.m_Age << endl;

}

int main(){

	test01();

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


	system("pause");
	return EXIT_SUCCESS;
}