仿定String类

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

int main()
{
    MyString s1("abc");
    MyString s2("ddd");
    cout << s1 + s2 << endl;
    cout << s1 << endl;
    cout << s2 << endl;

　　　s2 = "abc";
　　if (s1 == s2)
　　{
　　　　cout << "相等" << endl;
　　}
　　else
　　{
　　　　cout << "不相等" << endl;
　　}

return 0;
}
int main01()
{
    MyString s1("abc");
    MyString s3 = "123";
    MyString s2(s1);
    
    cout << s1 << endl;
    cout << s2 << endl;

    s1[1] = 'x';
    cout << s1 << endl;

    s3 = s1;
    cout << s3 << endl;

    cin >> s1;
    cout << s1 << endl;



    system("pause");
    return 0;
}

#include "MyString.h"

MyString::MyString()
{
    this->len = 0;
    this->str = NULL;
}

MyString::MyString(const char* str)
{
    if (str == NULL)
    {
        this->len = 0;
        this->str = new char[0 + 1];
        strcpy(this->str, "");
    }
    else
    {
        int len = strlen(str);
        this->len = len;
        this->str = new char[len + 1];
        strcpy(this->str, str);
    }
}
//初始化时候被调用的
MyString::MyString(const MyString &another)
{
    this->len = another.len;
    this->str = new char[this->len + 1];
    strcpy(this->str, another.str);
}
MyString::~MyString()
{
    if (this->str != NULL)
    {
        cout << this->str << "~MyString" << endl;
        delete this->str;
        this->str = NULL;
        this->len = 0;
    }
}


ostream& operator<<(ostream& os, MyString& s)
{
    os << s.str;
    return os;
}
char& MyString::operator[](int index)
{
    return this->str[index];
}
MyString& MyString::operator=(const MyString& another)
{
    if (this == &another)
    {
        return *this;
    }
    if (this->str != NULL)
    {
        delete[] this->str;
        this->str = NULL;
        this->len = 0;
    }
    this->len = another.len;
    this->str = new char[this->len + 1];
    strcpy(this->str, another.str);
    return *this;
}
istream& operator>>(istream& is, MyString & s)
{
    //将s字符串的空间 释放掉
    if (s.str != NULL)
    {
        delete[] s.str;
        s.str = NULL;
        s.len = 0;
    }
    //创建新的
    char temp_str[2048] = { 0 };
    cin >> temp_str;
    int len = strlen(temp_str);
    s.str = new char[len + 1];
    strcpy(s.str, temp_str);
    s.len = len;

    return is;
}
MyString MyString::operator+(MyString& another)
{
    MyString temp;

    int len = this->len + another.len;
    temp.len = len;
    temp.str = new char[len + 1];
    /*
    memset(temp.str, 0, len+1);
    strcat(temp.str, this->str);
    */

    strcpy(temp.str, this->str);
    strcat(temp.str, another.str);

    return temp;
}

bool MyString::operator==(MyString& another)
{
	if (this->len != another.len)
	{
		return false;
	}
	for (int i = 0; i < another.len; i++)
	{
		if (this->str[i] != another.str[i])
		{
			return false;
		}
	}

	return true;
}
//!=
bool MyString::operator!=(MyString& another)
{
	return !(*this == another);
}

　　

#pragma once
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
using namespace std;
class MyString
{
public:
    MyString();
    //MyString(int len); //创建一个长度为len的string
    MyString(const char* str);
    MyString(const MyString &another);
    ~MyString();
    //重载[]
    char& operator[](int index);
    //<<
    friend ostream& operator<<(ostream& os, MyString& s);
    //>>
    friend istream& operator>>(istream& is, MyString & s);
    //=
    MyString& operator=(const MyString& another);
    //+
    MyString operator+(MyString& another);
    //==

　　　　bool operator==(MyString& another);
　　　　//!=
　　　　bool operator!=(MyString& another);

private:
    int len;
    char *str;
};