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

Question

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)
20 5
1 5
28 5
2 5
20 5
4 5
22 5
88 3
27 5
34 5
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?

Answer 1

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...
}

Answer 2

You could model the input line with a struct:
struct Record
{
unsigned int m_age;
int m_favorite_number;
};
Then overload the operator>>:
struct Record
{
unsigned int m_age;
int m_favorite_number;
friend std::istream& operator>>(std::istream& input, Record& r);
};
std::istream& operator>>(std::istream& input, Record& r)
{
input >> r.m_age;
input >> r.m_favorite_number;
return input;
}
You could read in the data into a database by using:
std::vector<Record> database;
Record r;
while (std::cin >> r)
{
database.push_back(r);
}
In the above call, you could replace std::cin with a file stream.
You could print or display a record from the database:
std::cout << database[3].m_age << " " << database[3].m_favorite_number << "\n";
Although IMHO, you should overload operator<< to print the record in a default format.

Answer 3

Since you are using nameOfExecutable.exe < source.txt, you can use cin.eof to check if the end of file is reached:
while(true){
int a, b;
std::cin >> a;
if(std::cin.eof()){
break;
}
std::cin >> b;
//Create Class
}