量化交易之C++篇 - 字符串类的封装

// MyString.h
#pragma once

#include <iostream>
#include <string>

using namespace std;


class MyString {

  friend ostream& operator<<(ostream& cout, MyString& string);
  friend istream& operator>>(istream& cin, MyString& string);

public:
  MyString(const char* string);
  MyString(const MyString& myString);

  ~MyString();

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

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

  // 重载 +: 加号运算符重载后, 为什么少了两个析构函数? 因为重载中在堆区创建了两个新的对象，但是一直没有释放，那么应该在哪里释放？
  MyString& operator+(const char* string);
  MyString& operator+(const MyString& string);

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

private:
  char* pString;
  int size;
};

// MyString.cpp

#include "MyString.h"

MyString::MyString(const char* string) {
  
  cout << string << "  有参 构造函数" << endl;

  this->pString = new char[strlen(string) + 1];
  strcpy(this->pString, string);

  this->size = strlen(string);
}

MyString::MyString(const MyString& myString) {

  cout << myString.pString << "  copy 构造函数" << endl;

  this->pString = new char[strlen(myString.pString) + 1];
  strcpy(this->pString, myString.pString);

  this->size = myString.size;

}

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

MyString& MyString::operator=(const char* string)
{
  if (this->pString != NULL) {
    delete[] this->pString;
    this->pString = NULL;
  }

  this->pString = new char[strlen(string) + 1];
  strcpy(this->pString, string);
  this->size = strlen(string);

  return *this;
}

MyString& MyString::operator=(const MyString& string)
{
  if (this->pString != NULL) {
    delete[] this->pString;
    this->pString = NULL;
  }

  this->pString = new char[strlen(string.pString) + 1];
  strcpy(this->pString, string.pString);
  this->size = string.size;

  return *this;
}

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

MyString& MyString::operator+(const char* string) {
  int newSize = this->size + strlen(string) + 1;

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

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

  this->pString = temp;
  temp = NULL;

  return *this;
}

MyString& MyString::operator+(const MyString& string) {

  int newSize = this->size + (&string)->size + 1;

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

  strcat(temp, this->pString);
  strcat(temp, (&string)->pString);

  this->pString = temp;
  temp = NULL;

  return *this;
}

bool MyString::operator==(const char* string)
{
  return (strcmp(this->pString, string) == 0 && this->size == strlen(string));
}

bool MyString::operator==(const MyString& string)
{
  return (strcmp(this->pString, string.pString) == 0 && this->size == string.size);
}

ostream& operator<<(ostream &cout, MyString &string) {

  cout << string.pString;

  return cout;
}

istream& operator>>(istream& cin, MyString& string) {

  if (string.pString != NULL) {
    delete[] string.pString;
    string.pString = NULL;
  }

  char buffer[1024];
  cin >> buffer;

  string.pString = new char[strlen(buffer) + 1];
  strcpy(string.pString, buffer);
  string.size = strlen(buffer);

  cout << "string.pString: " << string.pString << endl;
  cout << "string.size: " << string.size << endl;

  return cin;
}

// C++ 的 .cpp文件
#include <iostream>
#include "MyString.h"

using namespace std;

void test01() {

  MyString string = "roger";

  cout << string << endl;

  cout << "请输入新的字符串: ";

  cin >> string;
}

void test02() {
  
  MyString stringRoger = "roger";

  MyString stringReiri(stringRoger);

  cout << stringReiri << endl;

  cout << stringRoger[2] << endl;
}

void test03() {
  MyString stringRoger = "roger";

  MyString stringReiri = "rei ri";

  MyString sum = stringRoger + stringReiri;

  // 重载 +: 加号运算符重载后, 为什么少了两个析构函数? 因为重载中在堆区创建了两个新的对象，但是一直没有释放，那么应该在哪里释放？
  cout << stringRoger + stringReiri << endl;
}

void test04() {

  MyString stringRoger1 = "roger";
  MyString stringRoger2 = "roger";

  MyString stringReiri = "rei ri";

  (stringRoger1 == stringRoger2) ? (cout << stringRoger1 << "==" << stringRoger2 << endl) : (cout << stringRoger1 << "!=" << stringRoger2 << endl);

  (stringRoger1 == stringReiri) ? (cout << stringRoger1 << "==" << stringReiri << endl) : (cout << stringRoger1 << "!=" << stringReiri << endl);
}


int main() {

  //test01();

  //test02();
  
  test03();

  //test04();

  return EXIT_SUCCESS;
}