Read class data from file : class save load « File Stream « C++ Tutorial






  1. C++ Tutorial
  2. File Stream
  3. class save load
#include <iostream>
using std::cerr;
using std::cout;
using std::endl;
using std::fixed;
using std::ios;
using std::left;
using std::right;
using std::showpoint;

#include <string>
using std::string;

#include <iomanip>
using std::setprecision;
using std::setw;

#include <fstream>
using std::ifstream;
using std::ostream;

#include <cstdlib>
using std::exit; // exit function prototype

class Account
{
public:
    Account(  )
    {
    }

    Account( int accountNumberValue, string lastNameValue, string firstNameValue, double balanceValue )
    {
       setAccountNumber( accountNumberValue );
       setLastName( lastNameValue );
       setFirstName( firstNameValue );
       setBalance( balanceValue );
    }

    int getAccountNumber() const
    {
       return accountNumber;
    }
    void setAccountNumber( int accountNumberValue )
    {
       accountNumber = accountNumberValue; // should validate
    }
    string getLastName() const
    {
       return lastName;
    }
    void setLastName( string lastNameString )
    {
       const char *lastNameValue = lastNameString.data();
       strncpy( lastName, lastNameValue, 5 );
       lastName[ 5 ] = '\0';
    }

    string getFirstName() const
    {
       return firstName;
    }

    void setFirstName( string firstNameString )
    {
       const char *firstNameValue = firstNameString.data();
       strncpy( firstName, firstNameValue, 5 );
       firstName[ 5 ] = '\0';
    }
    double getBalance() const
    {
       return balance;
    }
    void setBalance( double balanceValue )
    {
       balance = balanceValue;
    }

private:
   int accountNumber;
   char lastName[ 15 ];
   char firstName[ 10 ];
   double balance;
};


void outputLine( ostream&, const Account & ); // prototype

int main()
{
   ifstream inCredit( "credit.dat", ios::in );

   if ( !inCredit )
   {
      cerr << "File could not be opened." << endl;
      exit( 1 );
   } // end if

   Account client; // create record

   inCredit.read( reinterpret_cast< char * >( &client ), sizeof( Account ) );

   while ( inCredit && !inCredit.eof() )
   {
      if ( client.getAccountNumber() != 0 )
         outputLine( cout, client );

      inCredit.read( reinterpret_cast< char * >( &client ),sizeof( Account ) );
   }

   return 0;
}
void outputLine( ostream &output, const Account &record )
{
   output << left << setw( 10 ) << record.getAccountNumber()
      << setw( 16 ) << record.getLastName()
      << setw( 11 ) << record.getFirstName()
      << setw( 10 ) << setprecision( 2 ) << right << fixed
      << showpoint << record.getBalance() << endl;
}

1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20
1         AAAAA           BBBBB            1.20




12.4.class save load
12.4.1.Save class to a file
12.4.2.Writing a class to a file.
12.4.3.Read class data from file
12.4.4.Writing a Class to a File
12.4.5.Read person object from disk
12.4.6.saves person object to disk
12.4.7.reads and writes several objects to disk