c++從入門到精通——運算符重載（四）字符串類的封裝

字符串類的封裝

MyString.h

#pragma  once
#define  _CRT_SECURE_NO_WARNINGS
#include <iostream>
using namespace std;

class MyString
{
	friend ostream& operator<< (ostream& cout, MyString & str);
	friend istream& operator>> (istream& cin, MyString & str);
public:
	MyString(const char * str);
	MyString(const MyString & str);

	~MyString();

	//重載=運算符
	MyString& operator = (const char * str);
	MyString& operator=(const MyString & str);
	
	//重載[]運算符
	char& operator[](int index);

	//重載 +運算符
	MyString operator+(const char * str);
	MyString operator+(const MyString& str);

	//重載 == 運算符
	bool operator==(const char * str);
	bool operator==(const MyString & str);


private:
	char * pString; //執行堆區的指針
	int m_Size; // 字符串大小

};

MyString.cpp

#include "MyString.h"

ostream& operator<< (ostream& cout, MyString & str)
{
	cout << str.pString;
	return cout;
}

//右移運算符重載
istream& operator>> (istream& cin, MyString & str)
{
	//先判斷 原始是否有內容，如果有 清空
	if (str.pString != NULL)
	{
		delete [] str.pString;
		str.pString = NULL;
	}


	//讓用戶輸入內容
	char buf[1024];
	cin >> buf;

	//把用戶輸入的字符串 賦值給 str

	str.pString = new char[strlen(buf) + 1];
	strcpy(str.pString, buf);
	str.m_Size = strlen(buf);
	return cin;
}


MyString::MyString(const char * str)
{
	//cout << "有參構造調用" << endl;
	this->pString = new char[strlen(str) + 1];
	strcpy(this->pString, str);
	this->m_Size = strlen(str);
}

MyString::MyString(const MyString & str)
{
	this->pString = new char[strlen(str.pString) + 1];
	strcpy(this->pString, str.pString);
	this->m_Size = str.m_Size;
}

MyString::~MyString()
{

	//cout << "析構函數調用" << endl;
	if (this->pString != NULL)
	{
		delete[] this->pString;
		this->pString = NULL;
	}
}


char& MyString::operator[](int index)
{
	return this->pString[index];
}



MyString& MyString::operator=(const char * str)
{
	if (this->pString!=NULL)
	{
		delete[] this->pString;
		this->pString = NULL;
	}

	this->pString = new char[strlen(str) + 1];
	strcpy(this->pString, str);

	return *this;
}


MyString& MyString::operator=(const MyString & str)
{
	if (this->pString != NULL)
	{
		delete[] this->pString;
		this->pString = NULL;
	}

	this->pString = new char[strlen(str.pString) + 1];
	strcpy(this->pString, str.pString);

	return *this;
}


MyString MyString::operator+(const char * str)
{
	//計算返回的字符串開闢的大小
	int newSize = this->m_Size + strlen(str) + 1;

	char * tmp = new char[newSize];

	memset(tmp, 0, newSize);

	//拼接字符串
	strcat(tmp, this->pString);
	strcat(tmp, str);

	MyString newStr(tmp);
	delete[] tmp;
	return newStr;
}

MyString MyString::operator+(const MyString& str)
{

	int newSize = this->m_Size + strlen(str.pString) + 1;

	char * tmp = new char[newSize];

	memset(tmp, 0, newSize);

	//拼接字符串
	strcat(tmp, this->pString);
	strcat(tmp, str.pString);

	MyString newStr(tmp);
	delete[] tmp;
	return newStr;
}

bool MyString::operator==(const char * str)
{
	if ( strcmp( this->pString , str) == 0  && this->m_Size == strlen(str) )
	{
		return true;
	}
	return false;
			
}


bool MyString::operator==(const MyString & str)
{
	if (strcmp(this->pString, str.pString) == 0 && this->m_Size == strlen(str.pString))
	{
		return true;
	}
	return false;
}

測試

#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include "MyString.h"
using namespace std;

//測試 MyString
void test01()
{
	MyString str = "abc";

	cout << str << endl;

	/*cout << "請輸入str新的內容：" << endl;

	cin >> str;

	cout << "新內容爲：" << str << endl;*/

	MyString str2(str);

	MyString str3 = "aaaaaa";

	str3 = str2;
	str3 = "aaaa";

	cout << "str3 = " << str3 << endl;

	str3[0] = 'w';

	cout << "str3 第一個位置爲 = " << str3[0] << endl;


	MyString str4 = "";
	str4 = str2 + str3; //字符串拼接
	str4 = str2 + "kkk"; //字符串拼接

	cout << "str4 爲 " << str4 << endl;


	if (str3 == str4)
	{
		cout << "str3 與 str4相等" << endl;
	}
	else
	{
		cout << "str3 與 str4不相等" << endl;
	}

	/*int a = 10;
	cin >> a;
	cout << "a = " << a << endl;*/

}

int main(){

	test01();

	system("pause");
	return EXIT_SUCCESS;
}

運行

abc
str3 = aaaa
str3 第一個位置爲 = w
str4 爲 abckkk
str3 與 str4不相等