トレーニング--MyStringクラスの原則を強化

注：サブファイル書き込み

MyStrin.h

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

class MyString
{
	friend ostream& operator<<(ostream &cout,MyString& str);
	friend istream& operator>>(istream &cout,MyString& str);
public:
	MyString(const char * str);
	MyString(const MyString &str);
	~MyString();
	//重载=运算符
	void operator=(const char *str);
	void operator=(const MyString& str);
	//【】重载
	char& operator[](int index);
	//+重载
	MyString operator+(const char * str);
	MyString operator+(const MyString& str);
	//==重载
	bool operator==(const char * str);
	bool operator==(const MyString&str);

private:
	char * pString;
	int m_Size;
};

ostream& operator<<(ostream &cout,MyString& str);
istream& operator>>(istream &cout,MyString& str);

MyString.cpp

#include "MyString.h"

//构造
MyString::MyString(const char * str)
{
	cout<<"有参构造"<<endl;
	this->pString=new char[strlen(str)+1];
	strcpy(this->pString,str);
	this->m_Size=strlen(str);
}
//拷贝构造
MyString::MyString(const MyString &str)
{
	cout<<"拷贝构造调用"<<endl;
	this->pString = new char[str.m_Size+1];
	strcpy(this->pString,str.pString);
	this->m_Size=str.m_Size;
}
//析构
MyString::~MyString()
{
	cout<<"析构调用"<<endl;
	if(this->pString!=NULL)
	{
		delete [] this->pString;
		this->pString=NULL;
	}
}
//重载=运算符
void MyString::operator=(const char *str)
{
	if(this->pString!=NULL)
	{
		delete[] this->pString;
		this->pString=NULL;
	}

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

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

	this->pString=new char[str.m_Size+1];
	strcpy(this->pString,str.pString);
	this->m_Size=str.m_Size;
}

//重载【】运算符
char& MyString::operator[](int index)
{
	return this->pString[index];
}

//重载+运算符
MyString MyString::operator+(const char * str)
{
	char* tmp= new char[this->m_Size+strlen(str)+1];
	memset(tmp,0,this->m_Size+strlen(str)+1);
	strcat(tmp,this->pString);
	strcat(tmp,str);
	MyString str1(tmp);
	delete [] tmp;
	return str1;
}

MyString MyString::operator+(const MyString& str)
{
	char* tmp= new char[this->m_Size+str.m_Size+1];
	memset(tmp,0,this->m_Size+str.m_Size+1);
	strcat(tmp,this->pString);//strcat链接的顺序  tmp->Pstring->str.Pstring.
	strcat(tmp,str.pString);
	MyString str1(tmp);//做成一个对象
	delete [] tmp;
	return str1;
}

//重载==运算符
bool MyString::operator==(const char * str)
{
	//return this->pString==str;//错误，比较的是指针而不是字符串
	return !strcmp(this->pString,str);//返回的是相减的值，为0说明相等，返回1
}

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

ostream& operator<<(ostream &cout,MyString& str)
{
	cout<<str.pString;
	return cout;
}
istream& operator>>(istream &cout,MyString& str)
{
	//先释放str原有的空间
	if(str.pString!=NULL)
	{
		delete [] str.pString;
		str.pString=NULL;
	}
	//输入
	char buff[64];
	cin>>buff;
	//写入str中
	str.pString=new char[strlen(buff)+1];
	strcpy(str.pString,buff);
	str.m_Size=strlen(buff);
	return cin;
}

main.cの

#include<iostream>
#include"MyString.h"


void test01()
{
	MyString str("hello");
	cout <<str<<endl;

	MyString str1("哈哈哈");
	cout<<str1<<endl;

	//cout<<"请输入新内容：";
	//cin>>str1;
	//cout<<"输入后的新内容为："<<str1<<endl;

	//str1="hello";
	
	//cout<<str1<<endl;
	//cout<<str[0]<<endl;

/*	MyString str2=" ";
	str2=str+str1;
	cout<<str2<<endl*/;
	
	str1=str;
	cout <<str<<endl;
	cout<<str1<<endl;
	if(str1 == str)
	{
		cout<<"str1==str"<<endl;
	}
	else
	{
		cout<<"str1!=str"<<endl;
	}
}
int main()
{
	test01();
	return 0;
}