ifstream passed by reference to constructor can't be read - c++

Question

I don't understand why my ifstream can not be read in my class. In the main.cpp reading from the stream works fine, but when I pass the ifstream by reference to the c'tor I am not able to read from it. The program compiles fine but the 'inputfile' seems to be empty. In the console, I just see the content of my .txt once which comes from the main.cpp.
Am I doing something wrong with passing the ifstream?
main.cpp:
#include <iostream>
#include <fstream>
#include <string>
#include "RAM.h"
int main(int argc, char** argv)
{
std::ifstream input;
input.open("\\path\\orders.txt");
std::string line;
while (std::getline(input, line))
{
std::cout << line << std::endl;
}
RAM machine(input);
}
RAM.h:
#pragma once
#include <fstream>
class RAM
{
private:
std::ifstream& inputfile;
public:
RAM(std::ifstream&);
~RAM();
};
RAM.cpp:
#include "RAM.h"
#include <iostream>
#include <fstream>
#include <string>
RAM::RAM(std::ifstream &in) : inputfile(in){
std::string line;
while (std::getline(inputfile, line))
{
std::cout << line << std::endl;
}
}
RAM::~RAM() {
}
orders.txt:
ADD 5
SUB 7
HLT 99

Answer 1

The input file appears to be empty since you have already read all the data in main(). In other words, you're at the end of the file:
// File just opened, at position 0.
std::string line;
while (std::getline(input, line))
{
std::cout << line << std::endl;
}
// File fully read, at end of file.
RAM machine(input);
If you want to re-read it, you'll need to seek back to the start before attempting to re-read in the constructor, something like:
inputfile.seekg(0);