Passing a command line argument input file to a class to parse

Question

There is probably a very simple solution to my problem but I am having some problems passing an input file (from command line arguments) into a class for parsing.

Here is the relevant part of my main.cpp code:

#include <iostream>
#include <chrono>
#include "SortingCompetition.h"

int main(int argc, char** argv)
{
    if (argc != 3)
    {
        std::cerr << "Invalid arguments" << std::endl;
        std::cerr << "Usage: ./a.out <input file> <output file>" << std::endl;
        return 1;
    }

    SortingCompetition sorter(argv[1]);

    return 0;
}

Here is the SortingCompetition.h file:

#ifndef SORTINGCOMPETITION_H_
#define SORTINGCOMPETITION_H_

#include <string>
#include <vector>
using namespace std;

class SortingCompetition{
private:
    string& input_;
    vector<string> data_;
public:
    SortingCompetition(const string& inputFileName);
    void setFileName(const string& inputFileName);
    bool readData();
    bool prepareData();
    void sortData();
    void outputData(const string& outputFileName);
};

#endif

All the functions must remain the same here. i.e. SortingCompetition(const string& inputFileName); must stay that way... I cannot remove the const or anything else.

Here is the relevant implementation of SortingCompetition:

#include "SortingCompetition.h"

SortingCompetition::SortingCompetition(const string& inputFileName){
    input_ = inputFileName;
}
void SortingCompetition::setFileName(const string& inputFileName){
    input_ =  inputFileName;
}

This is where I'm getting problems, I'm not passing the input file from the command argument to the private variable correctly. I've searched for quite a while, but cannot find a solution.

What's the point where "parsing" is important? I don't think it's related. — sehe
– sehe, Commented Oct 2, 2013 at 18:36
In the readData function, I'm trying to parse the input file: bool SortingCompetition::readData(){ string temp; input_ >> temp; — tbgeorge
– tbgeorge, Commented Oct 2, 2013 at 18:39

sehe · Accepted Answer · 2013-10-02 18:32:42Z

2

You're passing it correctly, but you're storing a reference to temporary. This is the problem.

Change:

class SortingCompetition{
private:
    string input_;  // THIS LINE
    vector<string> data_;

This copies the value so it doesn't matter that the parameter to the constructor (or setFilename) was only a temporary

answered Oct 2, 2013 at 18:32

sehe

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1 Comment

tbgeorge Over a year ago

Ok, thanks. But what do I change it to? If I stick a const in there I can't parse it anymore.

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