40 C++ - 符号重载总结

=, [], () 和 -> 操作符只能通过成员函数进行重载

>只能通过全局函数配合友元函数进行重载

不要重载 && 和 || 操作符，因为无法实现短路规则

常规建议：

案例 - 字符串类封装

MyString.h

#define _CRT_SECURE_NO_WARNINGS
#pragma once
#include 
using namespace std;

class MyString
{
	friend ostream& operator(istream& in, MyString& str);

public:
	MyString(const char *);
	MyString(const MyString&);
	~MyString();

	char& operator[](int index); //[]重载

	//=号重载
	MyString& operator=(const char * str);
	MyString& operator=(const MyString& str); 

	//字符串拼接 重载+号
	MyString operator+(const char * str );
	MyString operator+(const MyString& str);

	//字符串比较
	bool operator== (const char * str);
	bool operator== (const MyString& str);
private:
	char * pString; //指向堆区空间
	int m_Size; //字符串长度 不算'\0'
};

MyString.cpp

#include "MyString.h"

//左移运算符
ostream& operator buf;

	str.pString = new char[strlen(buf) + 1];
	strcpy(str.pString, buf);
	str.m_Size = strlen(buf);

	return in;
}

//构造函数
MyString::MyString(const char * str)
{
	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)
{
	this->pString = new char[strlen(str.pString) + 1];
	strcpy(this->pString, str.pString);
	this->m_Size = str.m_Size;
}
//析构函数
MyString::~MyString()
{
	if (this->pString!=NULL)
	{
		delete[]this->pString;
		this->pString = NULL;
	}
}

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

MyString& 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);
	return *this;
}

MyString& MyString::operator=(const MyString& str)
{
	if (this->pString != NULL){
		delete[] this->pString;
		this->pString = NULL;
	}
	this->pString = new char[strlen(str.pString) + 1];
	strcpy(this->pString, str.pString);
	this->m_Size = str.m_Size;
	return *this;
}


MyString MyString::operator+(const char * str)
{
	int newsize = this->m_Size + strlen(str) + 1;
	char *temp = new char[newsize];
	memset(temp, 0, newsize);
	strcat(temp, this->pString);
	strcat(temp, str);

	MyString newstring(temp);
	delete[] temp;

	return newstring;
}

MyString MyString::operator+(const MyString& str)
{
	int newsize = this->m_Size + str.m_Size + 1;
	char *temp = new char[newsize];
	memset(temp, 0, newsize);
	strcat(temp, this->pString);
	strcat(temp, str.pString);

	MyString newstring(temp);
	delete[] temp;
	return newstring;
}

bool MyString::operator==(const char * str)
{
	if (strcmp(this->pString, str) == 0 && strlen(str) == this->m_Size){
		return true;
	}

	return false;
}

bool MyString::operator==(const MyString& str)
{
	if (strcmp(this->pString, str.pString) == 0 && str.m_Size == this->m_Size){
		return true;
	}

	return false;
}

TestMyString.cpp

void test01()
{
	MyString str("hello World");

	cout