string類作為例子詳解c++重載>>和<<

#include <iostream>
#include<string>
using namespace std;
class mystring{
public:
	mystring(const char *str = NULL);//普通構造函數 
	mystring(const mystring &other);//指派
	~mystring(void);
	mystring& operator=(const mystring &other);
	friend ostream& operator<<(ostream& out,mystring &str);
	friend istream& operator>>(istream& in,mystring &str);
	char *m_str;
};
mystring::mystring(const char *str){
	if(str==NULL){
		m_str=new char[1];
		*m_str='\0';
	}else{
		int len = strlen(str);
		m_str=new char[len];
	strcpy(m_str,str);
	}
}
mystring::mystring(const mystring &other){
		m_str=other.m_str;
}
mystring::~mystring(){
delete[] m_str;
}
mystring& mystring::operator=(const mystring &other){
m_str=other.m_str;
return *this;
}
ostream& operator<<(ostream& out,mystring &str){
	out<<str.m_str;
	return out;
}
istream& operator>>(istream& in,mystring &str){
	in>>str.m_str;
	return in;
}
int main(){
	mystring a;
	cin>>a;
	cout<<a<<endl;
return 0;
}