Question

I just want to read a text file and store the data into a vector. Thereby the value weight should be sum till the limit is reached. The first four lines will be read correctly but the following will not read. What is the mistake?

#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <limits>

/*
Data.txt 

John
6543
23

Max
342
2

A Team
5645
23
*/

struct entry
{
    // passengers data
    std::string name;
    int weight; // kg
    std::string group_code; 
};

void reservations()
{
    std::ofstream file;
    file.clear();
    file.open("reservations.txt");
    file.close();
}

entry read_passenger(std::ifstream &stream_in)
{
    entry passenger;
    if (stream_in)
    {
        std::getline(stream_in, passenger.name); 
        stream_in >> passenger.weight;
        std::getline(stream_in, passenger.group_code);
        stream_in.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
        return passenger;
    }

    return passenger; 
}

int main(void)
{
    std::ifstream stream_in("data.txt"); 
    std::vector<entry> v; // contains the passengers data
    const int limit_total_weight = 10000;   // kg
    int total_weight = 0;                   // kg
    entry current;
    while (!stream_in.eof())
    {
        current = read_passenger(stream_in);
        total_weight = total_weight + current.weight;
        std::cout << current.name << std::endl;
        if (total_weight >= limit_total_weight)
        {
            break;
        }

    }
        return 0;
}

Answer 1

These two lines,

    std::getline(stream_in, passenger.group_code);
    stream_in.ignore(std::numeric_limits<std::streamsize>::max(), '\n');

should be in the opposite order:

    stream_in.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
    std::getline(stream_in, passenger.group_code);

Think about what the purpose of the ignore is.

Also, instead of checking only for EOF, check for general error.

I.e., instead of

    while (!stream_in.eof())

write

    while (stream_in)

Maybe there’s more wrong, but the above is what I saw immediately.

Cheers & hth.,