virtualOperatorFileIO

#include <iostream>
#include <fstream>
#include <string>
#include <chrono>

class Parent
{
protected:
    int id;
public:
    Parent(int val = 0) : id{ val } {};
    virtual std::ostream& print(std::ostream& out)
    {
        if (typeid(out) == typeid(std::ofstream))
        {
            std::cout << "File I/O!!!\n";
            return out << 'P' << '\n' << id << '\n';
        }
        return out << "Parent id:" << id << '\n';
    };

    virtual std::istream& input(std::istream& in)
    {
        return in >> id;
    }

    virtual ~Parent() {};
    friend std::ostream& operator<<(std::ostream& out, Parent& obj);
    friend std::istream& operator>>(std::istream& in, Parent& obj);
};

std::ostream& operator<<(std::ostream& out, Parent& obj)
{
    return obj.print(out);
};

std::istream& operator>>(std::istream& in, Parent& obj)
{
    return obj.input(in);
};

class Child : public Parent
{
    std::string name;
public:
    Child(std::string str = "Child", int val = 0) : Parent{ val }, name{ str } {};
    virtual std::ostream& print(std::ostream& out)
    {
        if (typeid(out) == typeid(std::ofstream))
        {
            std::cout << "File I/O!!!\n";
            return out << 'C' << '\n' << id << '\n' << name << '\n';
        }
        return out << "Child id:" << id << " name:" << name << '\n';
    };

    virtual std::istream& input(std::istream& in)
    {
        return in >> id >> name;
    }

    void childWork() { std::cout << "Children " << name << " is working hard!\n"; };

    virtual ~Child() {};
};

int main()
{
    srand(time(0));

    Parent* objects[4];

    for (auto& object : objects)
    {
        object = (rand() % 2 ? new Parent : new Child);
    }

    for (auto& object : objects)
    {
        if (typeid(*object) == typeid(Child))
        {
            std::cout << "Input Child id and name\n";
        }
        else
        {
            std::cout << "Input Parent id\n";
        }
        std::cin >> *object;
    }

    std::ofstream outf{ "file.txt" };
    if (!outf.is_open())
    {
        std::cout << "Cannot create file! Exit now!\n";
    }

    for (auto& object : objects)
    {
        std::cout << *object;
        outf << *object;

        delete object;
    }

    outf.close();

    std::cout << "Now read file!\n";
    char buf[50];
    std::ifstream inf{ "file.txt" };

    if (!inf.is_open())
    {
        std::cout << "Cannot open file! Exit now!\n";
    }

    Parent fParent;
    Child fChild;

    std::string str;
    str.reserve(50);
    while (!inf.eof())
    {

        getline(inf, str);

        if (str == "P")
        {
            std::cout << "Got Parent!\n";
            inf >> fParent;
            std::cout << fParent << '\n';
        }

        if (str == "C")
        {
            std::cout << "Got Child!\n";
            inf >> fChild;
            std::cout << fChild << '\n';
        }

    }


    inf.close();
}