#pragma once
#ifndef __MY_STRING_H__
#define __MY_STRING_H__
#include <iostream>
using namespace std;class MyString
{
public:MyString();MyString(int len);MyString(const char* str);//拷贝构造函数MyString(const MyString &another);friend ostream& operator<<(ostream &cout, MyString& myString);friend istream& operator >> (istream &cin, MyString& myString);MyString& operator=(const MyString& another);char& operator[](int index);bool operator==(MyString& another);bool operator!=(MyString& another);MyString operator+(const MyString& myString);~MyString();private:int length;//实际字符个数char* str;
};
#endif // !__MY_STRING_H__

#include "MyString.h"MyString::MyString()
{this->length = 0;this->str = NULL;
}MyString::MyString(int len)
{//cout << "构造函数 MyString::MyString(int len)...." << endl;this->length = len;this->str = new char[len];//初始位空串memset(this->str, 0, len);
}
MyString::MyString(const char* str)
{//cout << "构造函数 MyString::MyString(const char* str)...." << endl;if (str == NULL){this->length = 0;this->str = new char[1];strcpy(this->str, "");return;}this->length = strlen(str);this->str = new char[this->length + 1];strcpy(this->str, str);}
//初始化时调用
MyString::MyString(const MyString & another)
{//cout << "拷贝构造函数 MyString::MyString(const MyString & another)...." << endl;this->length = another.length;this->str = new char[this->length+1];strcpy(this->str, another.str);
}MyString & MyString::operator=(const MyString & another)
{//cout << "赋值运算符 MyString & MyString::operator=(const MyString & another)...." << endl;// 防止自身赋值if (this == &another){return *this;}// 如果自身原来有空间，先释放if (this->str != NULL){delete[] this->str;this->str = NULL;this->length = 0;}// 新开辟空间进行内容拷贝this->length = another.length;this->str = new char[this->length + 1];strcpy(this->str, another.str);return *this;
}char& MyString::operator[](int index)
{return (this->str[index]);
}bool MyString::operator==(MyString & another)
{if (this == &another){return true;}if (this->length != another.length){return false;}if (strcmp(this->str, another.str) != 0){return false;}return true;
}bool MyString::operator!=(MyString & another)
{return !(*this==another);
}MyString MyString::operator+(const MyString& another)
{int len = this->length + another.length + 1;MyString str1(len);strcat(str1.str, this->str);strcat(str1.str, another.str);return str1;
}MyString::~MyString()
{//cout << "~MyString()" << endl;if (this->str != NULL){delete[] this->str;this->str = NULL;this->length = 0;}
}ostream & operator<<(ostream & cout, MyString & myString)
{if(myString.str!=NULL)cout << myString.str;return cout;
}istream & operator >> (istream & cin, MyString & myString)
{// 如果原来有字符串，将其清空if (myString.str != NULL){delete[] myString.str;myString.str = NULL;myString.length = 0;}//输入长度未知，用临时变量接收，然后进拷贝char temp[1024] = { 0 };cin >> temp;int len = strlen(temp);myString.length = len;myString.str = new char[len + 1];//注意：如果目标空间大于等于源字符串strcpy会复制到\0strcpy(myString.str, temp);return cin;
}

#define _CRT_SECURE_NO_WARNINGS
#include <cstdio>
#include <iostream>
#include "MyString.h"
using namespace std;int main(int argc, char *argv[])
{MyString str1("hello");//构造函数MyString str2("world");//构造函数//cout << str1 << str2 << endl;MyString str3 = str1;//调用拷贝构造函数cout << str3 <<endl;str3 = str2;// = 调用赋值运算符cout << str3 << endl;MyString str4 = str1 + str2;cout << str4 << endl;cout << "请重置str1和str2:";cin >> str1 >> str2;str4 = str1 + str2;cout << str4 << endl;MyString aa("aaa");MyString bb("aaa");cout <<"aa = " << aa<< ",bb = "<< bb <<",aa==bb:" << boolalpha << (aa == bb) <<endl;return 0;
}