简易String类的实现

小鱼儿 2022-05-14 22:18 197阅读 0赞

#ifndef MYSTRING_H
    #define MYSTRING_H
    #include <iostream>
    #include <stdlib.h>
    #include <cstring>
    //本质是对mystring的包装
    class MyString
    {
    private:
    	char* _buffer;
    	int _length;
    public:
    	/*MyString();*/
    	MyString(const char* str = nullptr);
    	MyString(const MyString& str);
    	MyString& operator=(const MyString& theMyString);
    	~MyString();
    
    	MyString operator+(const MyString& theMyString);
    	MyString& operator+=(const MyString& theMyString);
    
    	bool operator>(const MyString& theMyString);
    	bool operator<(const MyString& theMyString);
    	bool operator==(const MyString& theMyString);
    
    	char& operator[](int index);
    	char& at(int index);
    
    	char* c_str();
    
    	void printStr();
    };
    
    #endif

源文件:

#define _CRT_SECURE_NO_WARNINGS
    #include "MyString.h"
    
    //MyString::MyString() {
    //	_buffer = new char[1];
    //	*_buffer = '\0';  //设置一个空串
    //	_length = 0;
    //};
    
    MyString::MyString(const MyString& str) :_length{ str._length }, _buffer{ new char[str._length + 1] }
    {
    	strcpy_s(_buffer, _length + 1, str._buffer);
    }
    
    MyString::MyString(const char* str /*= nullptr*/)
    {
    	if (str == nullptr) {
    		_buffer = new char[1];
    		*_buffer = '\0';  //设置一个空串
    		_length = 0;
    	}
    	else {
    		_buffer = new char[strlen(str) + 1];
    		strcpy_s(_buffer, strlen(str) + 1, str);
    		_length = strlen(str);
    	}
    }
    
    MyString::~MyString() {
    	delete[] _buffer;
    };
    
    MyString MyString::operator+(const MyString& theMyString)   //若是新对象,不用传引用了
    {
    	int len = strlen(_buffer) + strlen(theMyString._buffer);
    	MyString newStr;
    	delete[] newStr._buffer;
    	newStr._buffer = new char[len + 1]{ 0 };  //要进行初始化
    	newStr._length = len;
    
    	strcat(strcat(newStr._buffer, this->_buffer),theMyString._buffer);   //starcat无法被赋值
    	return newStr;
    }
    
    MyString& MyString::operator+=(const MyString& theMyString)  //返回自身要返回引用
    {
    	//扩充空间
    	int catlen = strlen(this->_buffer);
    	int srclen = strlen(theMyString._buffer);
    	int len = catlen + srclen;
    	this->_buffer = static_cast<char*>(realloc(this->_buffer, len + 1));
    	//移动指针的首地址
    	memset(this->_buffer+catlen, 0, srclen+1);   //refresh后面多出来的空间
    	strcat(this->_buffer, theMyString._buffer);
    
    	//之前比较繁琐的方法
    	/*int len = strlen(_buffer) + strlen(theMyString._buffer);
    	MyString temp;
    	delete[] temp._buffer;
    	temp._buffer = new char[len + 1]{ 0 };
    	temp._length = len;
    	strcat(strcat(temp._buffer, this->_buffer), theMyString._buffer);
    
    	delete[] _buffer;
    	_buffer = new char[len + 1]{ 0 };
    	strcat(_buffer, temp._buffer);*/
    	
    	return *this;
    }
    
    bool MyString::operator>(const MyString& theMyString)
    {
    	return strcmp(this->_buffer,theMyString._buffer)>0;
    }
    
    bool MyString::operator<(const MyString& theMyString)
    {
    	return strcmp(this->_buffer, theMyString._buffer)<0;
    }
    
    bool MyString::operator==(const MyString& theMyString)
    {
    	return strcmp(this->_buffer, theMyString._buffer)==0;
    }
    
    //重载赋值运算符(基本格式)
    MyString& MyString::operator=(const MyString& theMyString) {
    
    	if (this != &theMyString) {   //这个this就是左值对象 Mystring*
    		delete[] _buffer;         //为了防止内存泄漏
    		_length = theMyString._length;
    		_buffer = new char[_length + 1];
    		strcpy_s(_buffer, _length + 1, theMyString._buffer);
    	}
    
    	return *this;
    }
    
    char& MyString::operator[](int index)
    {
    	return _buffer[index];
    }
    
    char& MyString::at(int index)
    {
    	return _buffer[index];
    }
    
    char* MyString::c_str()
    {
    	return _buffer;
    }
    
    void  MyString::printStr() {
    	std::cout << _buffer << std::endl;
    }