C++ Reading multiple integers from a text file - c++

Question

I'm a beginning C++ student and am having difficulty in getting my code to read multiple integers from a text file.
My task is to take pre existing code (the code I posted below) and modify it so instead of taking a user's input, it reads from a text file.
The main issue i'm having lies in the void getNumber function. It originally was just a simple cin statement that read 20 numbers input by the user, carried them into the main function, processed them in another function, then prints the results in the last one.
I have modified the code to read the text file successfully, however, it only reads the first value of the text file (ex text file reads: 1 2 3 4 ... 20) and the output reads: 1 1 1 1 1...
I've been looking up solutions for hours, unfortunately, a lot of the responses call for things I am not familiar with. It seems I will need to establish some type of loop? I'm unsure.
Thank you!
#include <iostream>
#include <iomanip>
#include <fstream>
using namespace std;
const int N = 20;
//Function prototypes
void initialize(int& zeroCount, int& oddCount, int& evenCount);
void getNumber(int& num);
void classifyNumber(int num, int& zeroCount, int& oddCount,
int& evenCount);
void printResults(int zeroCount, int oddCount, int evenCount);
int main ()
{
//Variable declaration
int counter; //loop control variable
int number; //variable to store the new number
int zeros; //variable to store the number of zeros
int odds; //variable to store the number of odd integers
int evens; //variable to store the number of even integers
initialize(zeros, odds, evens); //Step 1
cout << "Please enter " << N << " integers."
<< endl; //Step 2
cout << "The numbers you entered are: "
<< endl;
for (counter = 1; counter <= N; counter++) //Step 3
{
getNumber(number); //Step 3a
cout << number << " "; //Step 3b
classifyNumber(number, zeros, odds, evens); //Step 3c
}// end for loop
cout << endl;
printResults(zeros, odds, evens); //Step 4
return 0;
}
void initialize(int& zeroCount, int& oddCount, int& evenCount)
{
zeroCount = 0;
oddCount = 0;
evenCount = 0;
}
void getNumber(int& num)
{
ifstream inData;
inData.open("inputfile.txt");
inData >> num;
}
void classifyNumber(int num, int& zeroCount, int& oddCount,
int& evenCount)
{
switch (num % 2)
{
case 0:
evenCount++;
if (num == 0)
zeroCount++;
break;
case 1:
case -1:
oddCount++;
} //end switch
} //end classifyNumber
void printResults(int zeroCount, int oddCount, int evenCount)
{
ofstream outData;
outData.open("outputfile.txt.");
outData << "There are " << evenCount << " evens, "
<< "which includes " << zeroCount << " zeros"
<< endl;
outData << "The number of odd numbers is: " << oddCount
<< endl;
outData.close();
} //end printResults

Answer 1

The problem is that in the getNumber function you open the file every time it's called. That makes it start the reading from the beginning every time.

Answer 2

What happens is that you open the file every time inside of the getNumber function.
In doing so, you always start reading the file from the beginning. What you'd want to do is to read each time the next integer and not the same one. To do this you could open the file from the main function and pass the ifstream to the getNumber function.
int main ()
{
...
ifstream inpStream;
inpStream.open("inputfile.txt");
for (counter = 1; counter <= N; counter++) //Step 3
{
getNumber(number, inpStream); //Step 3a
cout << number << " "; //Step 3b
classifyNumber(number, zeros, odds, evens); //Step 3c
}// end for loop
return 0;
}
void getNumber(int& num, istream& inpStream)
{
inpStream >> num;
}
Notice that this way you can define inpStream to be cin and it will work too. That is because the getNumber function gets a reference to an istream (which cin is).