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一、程序及输出

1.1 头文件

myString.h

#pragma  once
#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
using namespace std;
class MyString
{
	//左移运算符友元
	friend ostream& operator<<(ostream & cout, MyString & str);
	//右移运算符 友元
	friend istream&  operator>>(istream & cin, MyString & str);
public:

	//有参构造
	MyString(char  * str);
	//拷贝构造
	MyString(const MyString & str);

	//重载=运算符 

	MyString& operator=(const char * str);
	MyString& operator=(const MyString & str);

	//重载[]运算符
	char& operator[](int index);

	//重载+运算符
	MyString operator+(const char * str);
	MyString operator+(const MyString&str);

	//重载==运算符 
	bool operator==(const char *str);
	bool operator==(const MyString &str);

	//析构
	~MyString();

private:

	char * pString; //维护在堆区开辟的字符数组

	int m_Size; //字符串长度 不统计"\0"

};

1.2 cpp文件

myString.cpp

#include "myString.h"

//重载左移运算符
ostream& operator<<(ostream & cout , MyString & str)
{
	cout << str.pString;
	return cout;
}

//重载右移运算符
istream&  operator>>(istream & cin, MyString & str)
{
	//先清空原来堆区数据
	if (str.pString)
	{
		delete[] str.pString;
		str.pString = NULL;
	}

	char buf[1024];//开辟临时数组 记录用户输入内容
	cin >> buf;

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

	return cin;
}

MyString::MyString(char * str)
{
	//cout << "MyString有参构造函数调用" << endl;
	this->pString = new char[strlen(str) + 1];
	strcpy(this->pString, str);
	this->m_Size = strlen(str);
}

MyString::MyString(const MyString & str)
{
	cout << "拷贝构造函数调用" << endl;
	this->pString =  new char[strlen(str.pString)+1];
	strcpy(this->pString, str.pString);
	this->m_Size = str.m_Size;
}

MyString& MyString::operator=(const char * str)
{
	//先判断原来堆区释放有内容，如果有先释放
	if (this->pString != NULL)
	{
		delete[]this->pString;
		this->pString = NULL;
	}

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

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

MyString MyString::operator+(const char * str)
{
	//本身 abc   传入 def
	//计算开辟内存大小
	int newSize = this->m_Size + strlen(str) + 1;

	char * temp = new char[newSize];
	memset(temp, 0, newSize);

	strcat(temp, this->pString);
	strcat(temp, str);

	MyString newString = temp;

	delete[] temp;

	return newString;
}

MyString MyString::operator+(const MyString&str)
{
	int newSize = this->m_Size + strlen(str.pString) + 1;

	char * temp = new char[newSize];
	memset(temp, 0, newSize);

	strcat(temp, this->pString);
	strcat(temp, str.pString);

	MyString newString = temp;

	delete[] temp;

	return newString;
}

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

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

MyString::~MyString()
{
	if (this->pString != NULL)
	{
		//cout << "析构调用" << endl;
		delete[] this->pString;
		this->pString = NULL;
	}

}

1.3 主程序

#include<iostream>
using namespace std;
#include "myString.h"


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

	cout << str << endl;

	cout << "请重新给str赋值：" << endl;

	cin >> str;

	cout << "str 新的值为： " << str << endl;

	MyString str2 = str;

	cout << "str2 = " << str2 << endl;
}

void test02()
{
	MyString str = "abcd";
	MyString str2 = "aaa";
	str2 = str;
	cout << "str2 = " << str2 << endl;
	cout << "str2[0] = " << str2[0] << endl;
	str2[0] = 'z';

	cout << "str2[0]改为z后输出：  " << str2 << endl;

	MyString str3 = "abc";
	MyString str4 = "def";
	MyString str5 = str3 + str4;
	MyString str6 = str5 + "ghe";
	cout << "str5 = " << str5 << endl;
	cout << "str6 = " << str6 << endl;

	if (str5 == str6)
	{
		cout << "str5 == str6" << endl;
	}
	else
	{
		cout << "str5 != str6" << endl;
	}

	if ( str6 == "abcdefghe")
	{
		cout << "str6 = abcdefghe" << endl;
	}
	else
	{
		cout << "str6 != abcdefghe" << endl;
	}
}


int main(){
	test01();
	test02();
	system("pause");
	return EXIT_SUCCESS;
}

输出：

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二、分析与总结

运算符重载的综合使用，方便整体回顾复习。