Read Data from File into Multiple Class Objects C++ - c++

Question

How do you create multiple new class objects using the default class constructor?
For a project I am having to write a program that writes three class objects into a file. That I have done... The next part is being able to read the data back into three separate class objects using a readData function and then displaying the data. I am completely lost at how to do this so I don't have any code in the readData function.
Here is an example of what the object looks like when it is being written to the file.
employee name(21, "first last", "45 East State", "661-9000", 30, 12.00);
Here is the bulk of my code the employee class is fairly basic but here is the default class constructor.
employee::employee ();
employee::employee(int locEmpNumber, string locName, string locaddress, string locphone, double locHrWorked, double locHrWage)
#include "employee.h"
#include <string>
#include <iomanip>
#include <iostream>
#include <fstream>
using namespace std;
void writeData (const employee& e);
void readData (const employee& e);
void printCheck (const employee& e);
int main( )
{
//Declarations
const int ONE = 1;
const int TWO = 2;
int userInput;
cout << "This program has two options:" << endl;
cout << "1 - Create a data files called 'EmployeeInfo.txt', or" << endl;
cout << "2 - Read data from a file and print paychecks." << endl;
cout << "Please enter (1) to create a file or (2) to print checks: ";
cin >> userInput;
if (userInput == ONE)
{
//Create employee objects:
employee joe(37, "Joe Brown", "123 Main St.", "123-6788", 45, 10.00);
employee sam(21, "Sam Jones", "45 East State", "661-9000", 30, 12.00);
employee mary(15, "Mary Smith", "12 High Street", "401-8900", 40, 15.00);
ofstream empFile ("EmployeeInfo.txt");
//Employee objects to write themselves out to the file.
writeData(joe);
writeData(sam);
writeData(mary);
//Close the file.
empFile.close();
//Print an message that creation of the file is complete.
system("CLS");
cout << "\nCreation of 'EmployeeInfo.txt' has completed.\n";
cout << "\nYou can now run option 2.\n";
//Exit.
system("PAUSE");
return 0;
}
else if (userInput == TWO)
{
//Create three new Employee objects, using the default Employee constructor.
//Open the file that you just saved.
//Have each object read itself in from the file.
//Call the printCheck( ) function for each of the three new objects, just as you did in the previous project.
}
else
{
system("CLS");
cout << "Incorrect entry.... Please try again and follow directions closely! \n" << endl;
system("PAUSE");
return 0;
}
}
void writeData(const employee& e)
{
fstream empFile;
empFile.open ("EmployeeInfo.txt", ios::app);
empFile << e.getEmpNumber() << "\n";
empFile << e.getName() << "\n";
empFile << e.getAddress() << "\n";
empFile << e.getPhone() << "\n";
empFile << e.getHrWorked() << "\n";
empFile << e.getHrWage() << "\n";
}
void readData(const employee& e)
{
fstream empFile;
empFile.open ("EmployeeInfo.txt", ios::in);
if(empFile.fail())
{
cout << "File could not be open. Please try option 1 then option 2.\n" << endl;
return;
}
}

Answer 1

It's good to see that you have made an effort at solving the problem. However, there is a mismatch between what you set out in your question and some of the comments in your code. It seems clear to me that a key part of your brief is that the employee object itself is required to be able to write itself to the file and to read itself back from the file.
You have written code that will write the contents of the object to the file rather than having the object write itself to the file. It might seem like I'm splitting hairs on this one, but this is the essence of what Object Oriented Programming is about. Encapsulating the functionality within the object itself is the real goal here.
I've included some code below to help you. Hopefully this will make good sense for you.
class employee
{
private:
int _locEmpNumber;
std::string _locName;
std::string _locAddress;
std::string _locPhone;
double _locHrWorked;
double _locHrWage;
public:
employee();
employee(int locEmpNumber, std::string locName, std::string locAddress, std::string locPhone, double locHrWorked, double locHrWage);
//object should be able to save itself as per your project brief.
void writeData(std::ofstream &empFile);
//object should be able to read itself from file as per your project brief
void readData(std::ifstream &empFile);
};
employee::employee()
{
_locEmpNumber = 0;
_locHrWorked = _locHrWage = 0;
}
employee::employee(int locEmpNumber, std::string locName, std::string locAddress, std::string locPhone, double locHrWorked, double locHrWage)
{
_locEmpNumber = locEmpNumber;
_locName = locName;
_locAddress = locAddress;
_locPhone = locPhone;
_locHrWorked = locHrWorked;
_locHrWage = locHrWage;
}
//
//From what I can glean from your brief ...
//Employee objects to write themselves out to the file!!!
void employee::writeData(std::ofstream &empFile)
{
empFile << _locEmpNumber << std::endl;
empFile << _locName << std::endl;
empFile << _locAddress<< std::endl;
empFile << _locPhone << std::endl;
empFile << _locHrWorked << std::endl;
empFile << _locHrWage << std::endl;
}
//
//Again, from what I can glean from your brief ...
//Have each object read itself in from the file!!!
void employee::readData(std::ifstream &empFile)
{
//Normally you would have error handling in a method like this and
//would either return a response that indicates that the operation
//succeded or failed. You might alternatively use exception handling
//or indeed a combination of both.
//
//Normally you would reset all members to initial / empty values before
//reading values into them from your file. In this case we will omit that
//for the purposes of simplicity. The main reason you would reset members
//is to ensure that when reusing an object you don't end up with partial
//data from the current "read" operation mixed with partial data that
//was already in the object before you started reading.
std::string inputStr;
std::getline(empFile, inputStr);
_locEmpNumber = atoi(inputStr.c_str());
std::getline(empFile, _locName);
std::getline(empFile, _locAddress);
std::getline(empFile, _locPhone);
std::getline(empFile, inputStr);
_locHrWorked = atof(inputStr.c_str());
std::getline(empFile, inputStr);
_locHrWage = atof(inputStr.c_str());
}
int main(int argc, char* argv[])
{
//Declarations
const int ONE = 1;
const int TWO = 2;
int userInput;
std::cout << "This program has two options:" << std::endl;
std::cout << "1 - Create a data files called 'EmployeeInfo.txt', or" << std::endl;
std::cout << "2 - Read data from a file and print paychecks." << std::endl;
std::cout << "Please enter (1) to create a file or (2) to print checks: ";
std::cin >> userInput;
if (userInput == ONE)
{
//Create employee objects:
employee joe(37, "Joe Brown", "123 Main St.", "123-6788", 45, 10.00);
employee sam(21, "Sam Jones", "45 East State", "661-9000", 30, 12.00);
employee mary(15, "Mary Smith", "12 High Street", "401-8900", 40, 15.00);
std::ofstream empFile ("EmployeeInfo.txt");
//Employee objects to write themselves out to the file.
joe.writeData(empFile);
sam.writeData(empFile);
mary.writeData(empFile);
// writeData(joe);
// writeData(sam);
// writeData(mary);
//Close the file.
empFile.close();
//Print an message that creation of the file is complete.
system("CLS");
std::cout << "\nCreation of 'EmployeeInfo.txt' has completed.\n";
std::cout << "\nYou can now run option 2.\n";
//Exit.
system("PAUSE");
return 0;
}
else if (userInput == TWO)
{
//Create three new Employee objects, using the default Employee constructor.
employee joe;
employee sam;
employee mary;
//Open the file that you just saved.
std::ifstream empFile("EmployeeInfo.txt");
//Have each object read itself in from the file.
joe.readData(empFile);
sam.readData(empFile);
mary.readData(empFile);
empFile.close();
//Call the printCheck( ) function for each of the three new objects, just as you did in the previous project.
//I'll leave it to you to add this yourself.
}
else
{
system("CLS");
std::cout << "Incorrect entry.... Please try again and follow directions closely! \n" << std::endl;
system("PAUSE");
return 0;
}
return 0;
}