自定義實現string類

Mystring.h

#pragma once
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
using namespace std;

class MyString {
public:
	MyString();
	//MyString(int len);
	MyString(const char *str);
	MyString(const MyString& other);//拷貝構造
	~MyString();

	//重載操作符[]
	char & operator[](int index);
	//重載操作符==
	bool operator==(const MyString& other);
	//重載操作符!=
	bool operator!=(const MyString& other);
	//重載操作符>
	bool operator>(MyString& other);
	//重載操作符<
	bool operator<(MyString& other);
	//重載操作符=
	MyString& operator=(const MyString &other);
	//重載操作符+
	MyString operator+(MyString& other);

	//重載操作符<<
	friend ostream& operator<<(ostream& os, MyString& s);
	//重載操作符>>
	friend istream& operator>>(istream& is, MyString& s);
private:
	int len;
	char *str;
};

Mystring.cpp 具體實現

#include "MyString.h"

MyString::MyString()
{
	this->len = 0;
	this->str = NULL;
}
//MyString(int len);
MyString::MyString(const char *str)
{
	if (str == NULL) {
		this->len = 0;
		this->str = new char[0 + 1];
		strcpy(this->str, "");
	}
	else {
		int length = strlen(str);
		this->len = length;
		this->str = new char[length + 1];
		strcpy(this->str, str);
	}
}
//拷貝構造在對象初始化賦值時調用，所有沒有垃圾需要清理
MyString::MyString(const MyString& other)
{
	this->len = other.len;
	this->str = new char[other.len + 1];
	strcpy(this->str, other.str);
}
MyString::~MyString()
{
	if (this->str != NULL) {
		cout << this->str << "執行了析構函數" << endl;
		delete this->str;
		this->str = NULL;
		this->len = 0;
	}
}
//重載操作符[]
char&  MyString::operator[](int index)
{
	return this->str[index];
}
//重載操作符==
bool MyString::operator==(const MyString& other)
{
	if (strcmp(this->str, other.str) == 0) {
		return true;
	}
	else {
		return false;
	}
}
//重載操作符!=
bool MyString::operator!=(const MyString& other)
{
	return !(*this == other);
}
//重載>
bool MyString::operator>(MyString& other)
{
	int ret = strcmp(this->str, other.str);
	if (ret > 0) {
		return true;
	}
	else {
		return false;
	}
}
//重載>
bool MyString::operator<(MyString& other)
{
	int ret = strcmp(this->str, other.str);
	if (ret < 0) {
		return true;
	}
	else {
		return false;
	}
}
//重載操作符=
MyString& MyString::operator=(const MyString &other)
{
	//1 如果是自身
	if (*this == other)
		return *this;
	//2 自身垃圾回收
	if (this->str != NULL) {
		delete[] this->str;
		this->str = NULL;
	}
	//3 賦值
	this->len = other.len;
	this->str = new char[this->len + 1];
	strcpy(this->str, other.str);
	return *this;
}
//重載操作符+
//返回匿名對象就可以進行連續+操作
MyString MyString::operator+(MyString& other)
{
	MyString temp;
	int len = this->len + other.len;
	temp.len = len;
	temp.str = new char[len + 1];
	memset(temp.str, 0, len + 1);
	strcat(temp.str, this->str);
	strcat(temp.str, other.str);
	return temp;
}
/*全局函數*/
//重載操作符<<
ostream& operator<<(ostream& os, MyString& s)
{
	os << s.str;
	return os;
}
//重載操作符>>
istream& operator>>(istream& is, MyString& s)
{
	//1 將s之前的字符串釋放掉
	if (s.str != NULL) {
		delete[] s.str;
		s.str = NULL;
		s.len = 0;
	}
	//2 通過cin添加新的字符串
	char temp_str[4096] = { 0 };//設定鍵盤輸入長度,用臨時變量來存儲輸入
	cin >> temp_str;
	int len = strlen(temp_str);
	s.str = new char[len + 1];
	strcpy(s.str, temp_str);
	s.len = len;
	return is;
}

main.cpp

#include "MyString.h"
int main()
{
	MyString s1("abc");
	MyString s2(s1);

	cout << "s1: " << s1 << endl;
	cout << "s2: " << s2 << endl;
	s1[0] = 'X';
	cout << "s1: " << s1 << endl;
	cout << "*******重載=******" << endl;
	MyString s3 = "123456";
	s1 = s3;
	cout << "s1: " << s1 << endl;
	cout << "*******重載cin>>******" << endl;
	cin >> s3;
	cout << "*******重載+******" << endl;
	cout << s1;
	s3 = s1 + s2;
	//cout << s3 + s1;
	return 0;
}