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Reading input from command line, separated by whitespace, into array of objects

March 25, 2022

I am experimenting with reading input from command line and successfully store them in objects attributes.

Example of input (./(nameOfExecutable) < (sourceText) in the command line)

I want to read and store them into object attributes.

experimentClass.h

#ifndef EXPERIMENTCLASS_H
#define EXPERIMENTCLASS_H

#pragma once

class experimentClass
{
public:
    experimentClass(int x, int y);
    ~experimentClass();

private:
    int age;
    int favoriteNumber;
};

#endif

experimentClass.cpp

#include "experimentClass.h"

experimentClass::experimentClass(int x, int y)
{   
    age = x;
    favoriteNumber = y;    
}

experimentClass::~experimentClass()
{

}

main.cpp

#include <iostream>
#include "experimentClass.h"
using namespace std;

int main(){
    
    int age;
    int favoriteNumber;

    std::cin >> age;
    std::cin >> favoriteNumber;
    experimentClass a(age, favoriteNumber);   
}

In this case, I am able to store 20 into a‘s age, 5 into a‘s favoriteNumber.

However, I want to do this process until it hits the end of input.

So, in this case, I want to create 10 objects with given input, using iteration, and store these object into an array or something.

How can I read them properly so that I can achieve this?

>Solution :

Simply take the logic you already have and put it inside a loop, eg:

#include <iostream>
#include <vector>
#include "experimentClass.h"
using namespace std;

int main() {
    
    int age;
    int favoriteNumber;
    vector<experimentClass> vec;

    while (cin >> age >> favoriteNumber) {
        experimentClass a(age, favoriteNumber);
        vec.push_back(a);
    }
   
    // use vec as needed...
}

Then you can take this a step further by implementing an operator>> for your class, eg:

#ifndef EXPERIMENTCLASS_H
#define EXPERIMENTCLASS_H

#include <istream>

#pragma once

class experimentClass
{
public:
    experimentClass(int x = 0, int y = 0);

    friend std::istream& operator>>(std::istream &is, experimentClass &cls);

private:
    int age;
    int favoriteNumber;
};

std::istream& operator>>(std::istream &is, experimentClass &cls);

#endif

#include "experimentClass.h"

experimentClass::experimentClass(int x, int y)
{   
    age = x;
    favoriteNumber = y;
}

std::istream& operator>>(std::istream &is, experimentClass &cls)
{
    return is >> cls.age >> cls.favoriteNumber;
}

#include <iostream>
#include <vector>
#include "experimentClass.h"
using namespace std;

int main() {
    
    experimentClass a;
    vector<experimentClass> vec;

    while (cin >> a) {
        vec.push_back(a);
    }
   
    // use vec as needed...
}