C++ MyString類的簡單實現

題目：string類的簡單實現，本文中此類名爲MyString

實現思路：

1 只要構造函數執行成功(其中pData_不爲空)

2 構造函數可通過char*,字符串常量構造

3 重載運算符=（返回值爲MyString），實現拷貝構造函數(深拷貝,返回值爲MyString&)

4 重載運算符<<,使之可通過cout輸出

5 實現字符串長度，字符串是否爲空函數

6 成員變量使用char* pData_保存字符串，使用int length_保存字符串長度

MyString.h

#pragma once
#include <iostream>


class MyString
{
public:
MyString(const char * pStr = nullptr);
MyString(const MyString& rhs);
~MyString();


bool empty();


MyString& operator=(const MyString& rhs);
MyString operator+(const MyString& rhs);
size_t size()
{
    return length_;
}


friend std::ostream& operator<<(std::ostream& os, const MyString &rhs);


private:
char *pData_;
size_t length_;
};


std::ostream& operator<<(std::ostream& os, const MyString &rhs);

MyString.cpp

#include "MyString.h"

#include <cstring>

MyString::MyString(const char *pStr)
{
	if (nullptr == pStr)
	{
		pData_ = new char[1];
		*pData_ = '\0';
		length_ = 0;
	}
	else
	{
		length_ = strlen(pStr);
		pData_ = new char[length_ + 1];
		strcpy(pData_, pStr);
	}
}

MyString::~MyString()
{
	if (nullptr != pData_)
	{
		delete pData_;
		pData_ = nullptr;
		length_ = 0;
	}
}

MyString::MyString(const MyString& rhs)
{
	if (nullptr == rhs.pData_)
	{
		pData_ = new char[1];
		*pData_ = '\0';
		length_ = 0;
	}
	else
	{
		length_ = rhs.length_;

		pData_ = new char[length_ + 1];
		strcpy(pData_, rhs.pData_);
	}
}

MyString& MyString::operator=(const MyString& rhs)
{
	if (this == &rhs)
	{
		return *this;
	}

	MyString newString(rhs);

	char*temp = newString.pData_;
	newString.pData_ = pData_;
	pData_ = temp;

	length_ = rhs.length_;

</pre><pre code_snippet_id="1557082" snippet_file_name="blog_20160115_4_9550508" name="code" class="cpp"><span style="white-space:pre">	</span>return *this;
}

MyString MyString::operator+(const MyString& rhs)
{
	MyString newString;
	
	if (length_ > 0 || rhs.length_ > 0)
	{
		char* temp = new char[length_ + rhs.length_ + 1];
		strcpy(temp, pData_);
		strcat(temp, rhs.pData_);
		delete newString.pData_;
		newString.pData_ = temp;
		newString.length_ = length_ + rhs.length_;
	}

	return newString;
}

bool MyString::empty()
{
	if (size() > 0)
	{
		return false;
	}
	else
	{
		return true;
	}
}


std::ostream& operator<<(std::ostream& os, const MyString &rhs)
{
	os << rhs.pData_;
	return os;
}

main.cpp 測試代碼

#include <iostream>

#include "MyString.h"
using namespace std;

int main()
{
	MyString str;
	cout << "str = "<< str << endl;
	if (str.empty())
	{
		cout << "str is empty" << endl;
	}
	else
	{
		cout << "str is not empty" << endl;
	}
	str = "fivestar";
	cout << "str = " << str << endl;
	if (str.empty())
	{
		cout << "str is empty" << endl;
	}
	else
	{
		cout << "str is not empty" << endl;
	}

	MyString str2 = " love a lot of girls";
	cout <<"str2.size() = "<< str2.size() << endl;
	cout << str + str2 << endl;

	

	
	return 0;
}