自定义 string类（C++）

#include <iostream>
using namespace std;

class MyString
{
public:
	friend ostream& operator<<(ostream& os, MyString& str);
	friend istream& operator>>(istream& is, MyString& str);

	MyString()
	{
		m_len = 0;
		m_str = nullptr;
	}

	//创建一个长度是len的string对象
	MyString(int len)
	{
		m_len = len;
		m_str = new char[m_len + 1];
		memset(m_str, 0, len + 1);
	}

	MyString(const char* str)
	{
		m_len = strlen(str);
		m_str = new char[m_len + 1];
		strcpy(m_str, str);
	}

	//拷贝构造函数
	MyString(const MyString& other)
	{
		if (nullptr != this->m_str)
		{
			delete this->m_str;
			this->m_str = nullptr;
		}

		this->m_len = other.m_len;

		this->m_str = new char[this->m_len + 1];
		strcpy(this->m_str, other.m_str);

	}

	~MyString()
	{
		if(nullptr == m_str)
		{
			return;
		}

		delete m_str;
		m_str = nullptr;
	}


	//[]操作符重载
	char operator[](int index)
	{
		char zimu = m_str[index];
		return zimu;
	}

	// = 运算符重载
	MyString& operator=(MyString& other)
	{	
		//避免自身赋值
		if(this == &other)
		{
			return *this;
		}

		this->m_len = other.m_len;
		this->m_str = new char[(this->m_len) + 1];
		strcpy(this->m_str, other.m_str);

		return *this;
	}

	// == 操作符重载
	bool operator==(MyString& other)
	{
		int ret = strcmp(this->m_str, other.m_str);

		if(ret == 0)
		{
			return true;
		}
		else
		{
			return false;
		}
	}

private:
	int m_len;
	char* m_str;
};

//cout操作符重载
ostream& operator<<(ostream& os, MyString& str)
{
	os << str.m_str;

	return os;
}

//cin 操作符重载
istream& operator>>(istream& is, MyString& str)
{
	if(nullptr != str.m_str)
	{
		delete str.m_str;
		str.m_str = nullptr;
	}

	char s[1024] = {0};

	cout << "请输入字符串：";
	cin >> s;

	str.m_len = strlen(s);
	str.m_str = new char[str.m_len + 1];
	strcpy(str.m_str, s);

	return is;
}


int main()
{

	MyString s1("hello world!");
	MyString s2(s1);

	cout << s2 << endl;

	return 0;
}