C++string类的简单实现

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#include<iostream>
#include<cstring>
using namespace std;
//C++实现string
class MyString
{
private:
	char* m_pData;
public:
	//构造函数
	MyString()
	{
		m_pData = new char[1];
		*m_pData = '\0';
	}
	//构造函数
	MyString(const char* str)
	{
		m_pData = new char[strlen(str) + 1];
		strcpy(m_pData, str);
	}
	//拷贝构造函数
	MyString(const MyString& other)
	{
		m_pData = new char[strlen(other.m_pData) + 1];
		strcpy(m_pData, other.m_pData);
	}
	//重载赋值运算符 = 
	MyString operator =(const MyString& other)
	{
		if (this != &other)
		{
			if (this->m_pData != NULL)
			{
				delete m_pData;
				m_pData = NULL;
			}
			m_pData = new char[strlen(other.m_pData) + 1];
			strcpy(m_pData, other.m_pData);
		}
		return*this;
	}
	//重载+运算符
	MyString operator +(const MyString& other)const
	{
		MyString newstring;
		if (this->m_pData == NULL)
		{
			newstring = other;
		}
		else if (other.m_pData == NULL)
		{
			newstring = *this;
		}
		else
		{
			newstring.m_pData = new char[strlen(this->m_pData) + strlen(other.m_pData) + 1];
			strcpy(newstring.m_pData, this->m_pData);
			strcat(newstring.m_pData, other.m_pData);
		}
		return newstring;
	}
	//重载下标运算符
	char& operator [](unsigned int index)
	{
		//进行下标的判断，看它是否有效
		if (index >= 0 && index < strlen(this->m_pData))
		{
			return this->m_pData[index];
		}
	}
	friend ostream& operator << (ostream& os, MyString& str);
	~MyString()
	{
		if (this->m_pData != NULL)
		{
			delete this->m_pData;
			this->m_pData = NULL;
		}
	}
};
//重载输出运算符<<
ostream& operator << (ostream& os, MyString& str)
{
	os << str.m_pData;
	return os;
}
int main(void)
{
	MyString str("Hello string");
	MyString str1;
	str1 = str;
	cout << str1 << endl;
	cout << str << endl;
	cout << str[2] << endl;
	return 0;
}