c++实现字符串类的封装

MyString.h文件

    #define  _CRT_SECURE_NO_WARNINGS
    #pragma once
    #include<iostream>
    #include<string>
    
    using namespace std;
    
    class MyString
    {
    	friend ostream & operator<<(ostream & cout, MyString & str);
    	friend istream & operator>>(istream &cin, MyString & str);
    public:
    	MyString(const char *);
    
    	MyString(const MyString & str);
    
    	~MyString();
    
    	//重载等号运算符
    	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+( char *str);
    	MyString  operator+( MyString & str);
    
    	//重载 == 运算符
    	bool operator ==(const char * str);
    	bool operator==(const MyString & str);
    
    private:
    	char * pString;//执行堆区指针
    	int m_Size; //字符串大小
    
    
    };

MyString.cpp文件

    #define  _CRT_SECURE_NO_WARNINGS
    #include"MyString.h"
    
    
    //左移运算符重载
    ostream & operator<<(ostream & cout, MyString & str)
    {
    	cout << str.pString;
    	return cout;
    }
    
    //右移运算符
    istream & operator>>(istream &cin, MyString & str)
    {
    	//先判断 原始是否有内容
    	if (str.pString != NULL)
    	{
    		delete[]str.pString;
    		str.pString = NULL;
    	}
    	//让用户输入内容
    	char buf[1024];
    	cin >> buf;
    	//把用户输入的字符串 赋值给str
    	str.pString = new char[strlen(buf) + 1];
    	strcpy(str.pString, buf);
    	str.m_Size = strlen(buf);
    	return cin;
    }
    
    
    MyString::MyString(const char * str)
    {
    	printf("有参构造调用\n");
    	this->pString = new char[strlen(str) + 1];
    	strcpy(this->pString, str);
    	this->m_Size = strlen(str);
    }
    
    MyString::MyString(const MyString & str)
    {
    	printf("拷贝构造调用\n");
    	this->pString = new char[strlen(str.pString) + 1];
    	strcpy(this->pString, str.pString);
    	this->m_Size = str.m_Size;
    }
    
    MyString::~MyString()
    {
    
    	//printf("析构调用\n");
    	if (this->pString != NULL)
    	{
    		delete[]this->pString;
    		this->pString = NULL;
    	}
    }
    
    
    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;
    }
    
    
    char & MyString::operator[](int index)
    {
    	return this->pString[index];
    }
    
    MyString MyString::operator+(const char * str)
    {
    	//计算返回的字符串开辟的大小
    	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)
    {
    	//计算返回的字符串开辟的大小
    	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 (str == NULL)
    	{
    		return false;
    	}
    	if (strcmp(this->pString, str) == 0 && this->m_Size == strlen(str))
    	{
    		return true;
    	}
    	return false;
    }
    
    bool MyString::operator==(const MyString & str)
    {
    	if (&str == NULL)
    	{
    		return false;
    	}
    
    	if (strcmp(this->pString, str.pString) == 0 && this->m_Size == strlen(str.pString))
    	{
    		return true;
    	}
    	return false;
    }

测试文件

    #include"MyString.h"	    
    void test01()
    {
    	MyString str = "abc";
    
    	cout << str << endl;
    	/*
    		cout << "请输入str新的内容" << endl;
    		cin >> str;
    		cout << "新内容为" << str<<endl;
    
    		*/
    	MyString str2(str);
    	MyString str3 = "aaaaaaaaa";
    	str3 = str2;
    	str3 = "aaaa";
    
    	cout << "str3=" << str3 << endl;
    
    	str3[0] = 'w';
    
    	cout << "str3第一个位置为" << str3[0] << endl;
    
    	MyString str4 = " ";
    	//str4 = str2 +str3;//字符串拼接
    
    	cout << "str4为" << str4 << endl;
    
    	if (str3 == str4)
    	{
    		cout << "str3与str4相等" << endl;
    	}
    	else
    	{
    		cout << "str3与str4不相等" << endl;
    	}
    }
    
    int main()
    {
    
    	test01();
    	system("pause");
    	return 0;
    }