C++ string 类 实现

string类默认生成的函数有哪些？

默认构造函数

析构函数

拷贝构造函数

赋值构造函数

 

具体实现如下：

#include <iostream>
using namespace std;

class mystring
{
	friend ostream &operator<<(ostream &out,const mystring &s);
public:
	mystring(const char *str=NULL);
	mystring(const mystring &rhs);
	~mystring();
	mystring &operator=(const mystring &other);
private:
	char *m_data;
};

//默认构造函数
mystring::mystring(const char *str)
{
	cout << "默认构造函数调用啦。"<<endl;
	if(NULL == str)
	{
		m_data=NULL;
	}
	else
	{
		m_data = new char[strlen(str)+1];
		strcpy(m_data,str);
	}
}

//拷贝构造函数
mystring::mystring(const mystring &rhs)
{
	cout << "拷贝构造函数嗲用啦"<<endl;
	if(rhs.m_data == NULL)
	{
		this->m_data = NULL;
	}
	else
	{
		this->m_data = new char[strlen(rhs.m_data)+1];
		strcpy(this->m_data,rhs.m_data);
	}
}

//析构函数
mystring::~mystring()
{
	cout << "析构调用啦！！"<<endl;
	if(this->m_data != NULL)
	{
		delete [] this->m_data;
		this->m_data = NULL;
	}
}

//赋值操作符重载
mystring &mystring::operator =(const mystring &other)
{
	cout << "调用赋值操作符了。"<<endl;
	if(this != &other)
	{
		delete [] this->m_data;
		if(!other.m_data)
		{
			this->m_data = NULL;
		}
		else
		{
			this->m_data = new char[strlen(other.m_data)+1];
			strcpy(this->m_data,other.m_data);
		}
	}
	else
	{
		return *this;
	}
}
//友元函数----输出操作符
ostream &operator<<(ostream &os,const mystring &s)
{
    os << s.m_data;
    return os;
}


void main()
{
	mystring m("hello");//调用默认构造函数
	mystring b = m;//调用赋值操作符
	cout << b <<endl;
}