Writing object array contents to and from file - c++

Question

I am currently trying to write a section of my program to read objects from an array into a text file and vice versa. I can get it to output objects to a file with seemingly no issues, but when I try to read data in from the text file into an empty array, it places the last object where the first one should be and leaves all others blank. Where am I going wrong? Here is my class code
//Defining function for items to file
void Stock::writeToFile(ofstream& fileOut)
{
fileOut << stockCode << " ";
fileOut << stockDesc << " ";
fileOut << currentLevel << " ";
fileOut << reorderLevel << " ";
}
//Defining function for reading items in from the file
void Stock::readFromFile(ifstream& fileIn)
{
while (fileIn >> stockCode >> stockDesc >> currentLevel >> reorderLevel)
{
fileIn >> stockCode;
fileIn >> stockDesc;
fileIn >> currentLevel;
fileIn >> reorderLevel;
}
}
And this is my code in main
#include <iostream>
#include <string>
#include <fstream>
#include "Stock.h"
using namespace std;
int main()
{
Stock items[4];
int option = 0;
cout << "1.Display full stock list." << endl;
cout << "Please pick an option: ";
cin >> option;
switch (option)
{
case 1:
cout << "stockCode" << '\t' << "stockDesc" << '\t' << '\t' << "CurrentLevel" << '\t' << "ReorderLevel" << endl;
cout << "------------------------------------------------------------------------------" << endl;
ifstream fileIn;
fileIn.open("Stock.txt");
for (int i = 0; i < 4; i++)
{
items[i].readFromFile(fileIn);
cout << items[i].getCode() << '\t' << '\t';
cout << items[i].getDescription() << '\t' << '\t' << '\t';
cout << items[i].getCurrentLevel() << '\t' << '\t';
cout << items[i].getReorderLevel() << endl;
}
}
return 0;
}

Answer 1

This loop runs through the entire file until it can't read any more, which is why the last set of variables is only one visible. All the ones prior are overwritten.
while (fileIn >> stockCode >> stockDesc >> currentLevel >> reorderLevel)
{
fileIn >> stockCode;
fileIn >> stockDesc;
fileIn >> currentLevel;
fileIn >> reorderLevel;
}
First time in your for loop, the call
items[i].readFromFile(fileIn);
cycles through the entire file. All the remaining iterations in your for loop, try to read from the file, but it's already at EOF.

Answer 2

As molbdnilo pointed out you want to read from file into your stock object sequentially so the loop should be removed. Also in this case it is better to have custom friend functions to read and write from streams into your object directly. See code below that can accomplish that.
#include <iostream>
#include <fstream>
#include <string>
// This what goes into your "Stock.h"
class Stock{
std::string stockCode;
std::string stockDesc;
int currentLevel;
int reorderLevel;
public:
Stock():currentLevel(0),reorderLevel(0){};
Stock(std::string const & scode,
std::string const & sdesc,
int const clevel,
int const rlevel
):stockCode(scode),
stockDesc(sdesc),
currentLevel(clevel),
reorderLevel(rlevel){}
friend std::istream& operator >>(std::istream& is, Stock& stk)
{
if (is) {
is
>> stk.stockCode
>> stk.stockDesc
>> stk.currentLevel
>> stk.reorderLevel;
}
return is;
}
friend std::ostream& operator <<(std::ostream& os, Stock const& stk)
{
os
<< stk.stockCode << ' '
<< stk.stockDesc << ' '
<< stk.currentLevel << ' '
<< stk.reorderLevel
<< '\n' //Line break after every object so that you can open and read.
;
}
};
//This is your main code with the read loop fixed.
int main()
{
const int N = 4;
Stock items[N];
//1. Create 4 Stock objects.
items[0] = Stock("A", "STKA", 100, 100);
items[1] = Stock("B", "STKB", 101, 101);
items[2] = Stock("C", "STKC", 102, 102);
items[3] = Stock("D", "STKD", 103, 103);
//2. Write the 4 Stock objects to a file.
std::ofstream ofs;
ofs.open("Stock.txt", std::ofstream::out);
for ( int i = 0; i < N ; ++i ) {
ofs << items[i] ;
}
ofs.close();
// 3. Read from the file written in 2. and print.
std::ifstream fileIn;
fileIn.open("Stock.txt");
Stock stk;
while (fileIn >> stk) {
std::cout << stk;
}
fileIn.close();
}
And the output is:
A STKA 100 100
B STKB 101 101
C STKC 102 102
D STKD 103 103

Answer 3

You're reading the entire file into the first Stock, and you're even reading each Stock's data twice.
The remainder of the stocks fail because you've reached the end of the file.
Remove the loop from readFromFile.

Answer 4

For each item, you are looping until the end of file is reached in Stock::readFromFile(). You need to remove the loop there:
//Defining function for reading items in from the file
void Stock::readFromFile(ifstream& fileIn)
{
fileIn >> stockCode;
fileIn >> stockDesc;
fileIn >> currentLevel;
fileIn >> reorderLevel;
}
So, there was nothing left to read for the remaining items.