String类操作的重载实现

string 类操作的重载实现

class CMyString
{
public:
	CMyString(char *ptr = NULL)
	{
		if (ptr == NULL)
		{
			mpStr = new char[1];
			*mpStr = '\0';
		}
		else
		{
			mpStr = new char[strlen(ptr) + 1];
			strcpy(mpStr, ptr);
		}
	}
	~CMyString()
	{
		delete[]mpStr;
		mpStr = NULL;
	}
	CMyString(const CMyString &src)
	{
		mpStr = new char[src.length() + 1];
		strcpy(mpStr, src.mpStr);
	}
	CMyString& operator=(const CMyString &src)
	{
		if (this == &src)
		{
			return*this;
		}
		delete[]mpStr;
		mpStr = NULL;
		mpStr = new char[src.length() + 1];
		strcpy(mpStr, src.mpStr);
		return *this;
	}
	bool operator>(const CMyString&src){ return strcmp(mpStr, src.mpStr) > 0; }
	bool operator<(const CMyString&src){ return strcmp(mpStr, src.mpStr) < 0; }
	bool operator==(const CMyString&src){ return strcmp(mpStr, src.mpStr) == 0; }
	bool operator!=(const CMyString&src){ return strcmp(mpStr, src.mpStr) != 0; }
	char operator[](int index)
	{
		return  mpStr[index];
	}
	int length()const{ return strlen(mpStr); }
	const char* c_str()const{ return mpStr; }

	// 定义当前CMyString类型的迭代器
	class iterator
	{
	public:
		iterator(char *ptr = NULL) :_ptr(ptr){}

		/*iterator(char *ptr = NULL, int pos = 0)
		{
			_ptr = _ptr + pos;
		}*/

		// 构造函数  operator!=   operator++   operator*
		bool operator!=(const iterator &it)
		{
			return _ptr != it._ptr;
		}
		void operator++()
		{
			_ptr++;
		}
		char& operator*() 
		{
			return *_ptr;
		}
	private:
		// 迭代器的成员变量
		char *_ptr;
	};
	iterator begin(){ return iterator(mpStr); }  // return第0号位元素的迭代器表示
	iterator end(){ return iterator(mpStr + length()); } // return最后一位元素的迭代器表示

private:
	char *mpStr;

	friend CMyString operator+(const CMyString &lhs,const CMyString &rhs);
	friend ostream& operator<<(ostream&out, const CMyString&src);
	friend istream& operator>>(istream&in, CMyString&src);

};

CMyString operator+(const CMyString &lhs, const CMyString &rhs)
{
	char*ptmp = new char[lhs.length() + rhs.length() + 1];
	strcpy(ptmp, lhs.mpStr);
	strcat(ptmp, rhs.mpStr);
	CMyString tmp(ptmp);
	delete ptmp;
	return tmp;
}
ostream& operator<<(ostream&out, const CMyString&src)
{
	out << src.mpStr << endl;
	return out;
}
istream& operator>>(istream&in, CMyString&src)
{
	char buff[1024] = {0};
	in >> buff;
	delete[]src.mpStr;
	src.mpStr = new char[strlen(buff) + 1];
	strcpy(src.mpStr, buff);
	return in;
}
// operator<<   operator>>
int main()
{
	CMyString str1;
	CMyString str2 = "aaa";
	CMyString str3 = "bbb";
	CMyString str4 = str2 + str3;
	cout << str4 << endl;
	str4 = str2 + "ccc";
	cout << str4 << endl;
	str4 = "ddd" + str2;
	cout << str4 << endl;
	cout << "请输入一段字符串:";
	cin >> str4;
	cout << "你输入的字符串是:" << str4 << endl;

	if (str2 > str3)
	{
		cout << "str2 > str3" << endl;
	}
	else
	{
		cout << "str2 <= str3" << endl;
	}

	int size = str4.length();
	for (int i = 0; i < size; ++i)
	{
		cout << str4[i];
	}
	cout << endl;

	char buffer[1024] = { 0 };
	strcpy(buffer, str4.c_str());
	cout << "buffer:" << buffer << endl;

	CMyString testStr = "hello world";
	CMyString::iterator it = testStr.begin(); // begin()返回第0个元素的迭代器
	for (; it != testStr.end(); ++it)// testStr.end()返回最后一个元素的后继位置
	{
		cout << *it << " ";
	}
	cout << endl;

	return 0;
}

运行结果如下：