How would i file handle objects(store / import) in C++

Question

Petroleum test = Set_Petroleum_values();
    ofstream fuel("Fuel.txt");
    {
        fuel << test << " ";
        fuel.close();
    }

the set values function takes the users input and calls a default constructor for the test object. My aim here is to somehow save the info that is being stored into this object however i am not sure how would i overload the "<<" operator when it comes to file handling. and yes the aim is to store the object so that the info is maintained once different operations and functions are proceeded etc.

Answer 1

I think you should overload << operator in Petroleum class like this :

#include <iostream>
#include <fstream>

class Petroleum
{
public:
    Petroleum(int v1,int v2) : val1(v1), val2(v2) {}
    friend std::ostream& operator<<(std::ostream& os, const Petroleum& pet);
private:
    int val1;
    int val2;
};

std::ostream& operator<<(std::ostream& os, const Petroleum& pet)
{
    return os << pet.val1 << " " << pet.val2 << std::endl;
}

int main()
{
    Petroleum pet(2, 3);

    std::ofstream fuel("Fuel.txt");
    fuel << pet;
    fuel.close();
}