自定义string

#include "MyString.h"//自定义stringMyString::MyString(){this->len = 0;this->str = NULL;}MyString::MyString(int len){if (len == 0) {this->len = 0;this->str = new char[len + 1];strcpy(this->str, "");}else {this->len = len;this->str = new char[len + 1];//多一个\0空间memset(this->str, 0, len + 1);}}MyString::MyString(const char * str){cout << "MyString(const char * str)" << endl;if (str == NULL) {this->len = 0;this->str = new char[len + 1];strcpy(this->str, "");}else {int len = strlen(str);this->len = len;this->str = new char[len + 1]; //开辟str的空间长度strcpy(this->str, str); //将str拷贝给this->str}}MyString::MyString(const MyString& another){cout << "MyString(const MyString& another)" << endl;//深拷贝this->len = another.len;//拷贝strthis->str = new char[len + 1];strcpy(this->str, another.str);}MyString &  MyString::operator=(const MyString& another){cout << " MyString::operator= ..." << endl;//判断是否是自身if (this == &another) {return *this;}//之前是否有垃圾回收if (this->str != NULL) {delete[]this->str;this->str = NULL;this->len = 0;}//深拷贝this->len = another.len;this->str = new char[len + 1];strcpy(this->str, another.str);//返回自身return *this;}MyString::~MyString(){if (this->str != NULL) {cout << "~MyString()..." << endl;delete[]this->str;this->len = 0;this->str = NULL;}}char& MyString::operator[](int index){return this->str[index];}MyString & MyString::operator+=(MyString &another){//如果另一个字符串是空字符串if (another.len == 0) {return *this;}else if (this->len == 0) {*this = another;return *this;}//两边都不是空字符串//"123"   "abc"//"123abc"char *old_str = this->str;//将之前的str的堆内存地址保存下来，以备释放//求出新字符串的长度int len = this->len + another.len;this->str = new char[len + 1];strcpy(this->str, old_str);strcat(this->str, another.str);if (old_str != NULL) {delete[]old_str;}return *this;}MyString & MyString::operator += (char *str){return *this;}bool MyString::operator>(MyString &another){int ret = strcmp(this->str, another.str);if (ret > 0) {return true;}else {return false;}}bool MyString::operator<(MyString &another){int ret = strcmp(this->str, another.str);if (ret < 0) {return true;}else {return false;}}ostream& operator<<(ostream &os, MyString &string){if (string.str != NULL) {os << string.str;}return os;}istream &operator>>(istream &is, MyString &string){//回收之前的数据if (string.str != NULL) {delete[]  string.str;string.str = NULL;string.len = 0;}char buf[4096] = { 0 };cout << "请输入一个字符串小于4096" << endl;cin >> buf;string.len = strlen(buf);string.str = new char[string.len + 1];strcpy(string.str, buf);return is;}