用string实现的一个完整的类，包含以下操作：重载运算符 > >，< < ，string模板类，fstream对二进制数据读写

///// 一个完整的类，包含以下操作：重载运算符 << >>，赋值转换，string模板类，fstream对二进制数据读写

#include <iostream>
#include <fstream>
#include <string>

using namespace std;

class Tperson;          // declaration of Tperson class
ostream& operator << (ostream& s, Tperson& per);   // declaration of function
istream& operator >> (istream& s, Tperson& per);    // declaration of function

class Tperson
{
     friend ostream& operator << (ostream& s, Tperson& per);  //friend declartion
     friend istream& operator >> (istream& s, Tperson& per);   //friend declartion
     string _name;          //_name is Tperson's name
     public:
            Tperson (string n = "") { _name = n; }  //default constructor
            Tperson (const Tperson& per) { _name = per._name; } //copy constructor
            Tperson& operator = (const Tperson& per) { _name = per._name; return *this; }    //overrding assignment function //有必要进行定义，这是对象的赋值，不产生临时对象
            //Tperson& operator = (string strSrc) { _name = strSrc; return *this; } //overrding assignment function 定义了构造函数就无需定义赋值转换了，会自动调用构造函数，产生临时对象，和前一个不同
            void Setname (string n) { _name = n; } //set Tperson's name
            string Getname () const { return _name; }  //get Tperson's name
};
ostream& operator << (ostream& s, Tperson& per)  //definition of overriding << function
{
           s << per._name;
           return s;
}
istream& operator >> (istream& s, Tperson& per)  //definition of overriding >> function
{
           s >> per._name;
           return s;
}

//funtion to verify class Tperson
void File ()
{
           Tperson per1[3] = {Tperson ("P11"),Tperson ("P2"),Tperson ("P3")};
 
           //write binary file
           ofstream outfile;
           outfile.open ("c://data.dat", ios::binary); 
           for (int i = 0; i < 3; i++)
           outfile.write ((char*)&per1[i], sizeof (per1[i]));
           outfile.close ();

           //read binary file
           ifstream infile ("c://data.dat", ios::binary);
           if (!infile)
           {
                      cerr << "文件无法打开";
                      exit (1);
           }
           Tperson per2[3]; 
           for ( i = 0; i < 3; i++)
           infile.read ((char*)&per2[i], sizeof (per2[i]));
           infile.close ();
           for ( i = 0; i < 3; i++)
           {
                      cout << "name : " << per2[i].Getname () << " " << sizeof (per2[i]) << " " << sizeof (Tperson) << endl;
           }

           //verify overriding and assignment functions
           Tperson per ("sfg");             cin >> per;
           cout << per<< endl;;
           per = "LKH:KHG";    //赋值，将产生临时对象
           cout << per << endl;
           per = per2[2];
           cout << per << endl;
           Tperson per3 = Tperson ("Hey");   //强制转换
}