实现C++类中默认的四个方法默认构造函数、析构函数、拷贝构造函数、赋值函数

#ifndef _BASECLASS_H_
#define _BASECLASS_H_

#include <iostream>
using namespace std;

#define NUMBER  100

class Base
{
public:
Base();                           //默认构造函数
Base(const char *data);            //override构造函数
Base(const Base & base);           //拷贝构造函数
Base& operator=(const Base &base);  //赋值函数
Base* operator&();                 //取地址运算符
//const Base* operator&();           //const类型取地址运算符
~Base();                          //析构函数
private:
char * m_data;
};

#endif _BASECLASS_H_

#include "BaseClass.h"

/*默认无参构造函数实现*/
Base::Base()
{
if (m_data == NULL)
{
m_data = new char[1];
*m_data = '\0';
}
cout<<"construct function."<<endl;
}

/*默认构造函数实现*/
Base::Base(const char *data)
{
_ASSERT(NULL != data);
m_data = NULL;
m_data = new char[strlen(data) + 1];
if (NULL == m_data)
{
_ASSERT(0);
}
memset(m_data, NULL, sizeof(m_data));
memcpy(m_data, data, strlen(data));
m_data[strlen(data)] = '\0';
cout<<"copy construct function::"<<m_data<<endl;
}

/*默认拷贝构造函数实现*/
Base::Base(const Base &base)
{
m_data = new char[strlen(base.m_data) + 1];
if (NULL == m_data)
{
_ASSERT(0);
}
memset(m_data, NULL, sizeof(m_data));
memcpy(m_data, base.m_data, strlen(base.m_data));
m_data[strlen(base.m_data)] = '\0';
cout<<"voluation construct function::"<<m_data<<endl;
}

/*默认重载'='赋值操作符函数实现*/
Base & Base::operator=(const Base &base)
{
_ASSERT(NULL != base.m_data);
if (this == &base)
{
return *this;
}
delete []m_data;  //这儿只将内容删除掉，字符串指针保留
m_data = new char[strlen(base.m_data) + 1];
if (NULL == m_data)
{
_ASSERT(0);
}
memset(m_data, NULL, sizeof(m_data));
memcpy(m_data, base.m_data, strlen(base.m_data));
m_data[strlen(base.m_data)] = '\0';
cout<<"Copy assignment operator construct function::"<<m_data<<endl;
return *this;
}

/*默认析构函数实现*/
Base::~Base()
{
cout<<"destructor function."<<endl;
delete []m_data;
m_data = NULL;
}

#include "BaseClass.h"

int main()
{
//Base base("hello world!");
Base base = Base("hello world!");
Base copybase(base);     //此处调用的是默认拷贝构造函数，因为是在定义的时候赋值，所以来不及调用'='赋值操作符
//与后面的操作是等价的：Base copybase=base; 或 Base copybase = Base(base);
Base copy2base;
copy2base=base;         //已经初始化完成，调用的是'='赋值操作符
copy2base.~Base();
copybase.~Base();
base.~Base();
return 0;
}