Сериализация custom обьектов, которые имеют общего родителя и поле другого класса

class Time
{
    int year;
    int month;
    int day;
public:
    ostream& serialize(ostream& os);
    istream& unserialize(istream& is);
 
    void set(int y, int m, int d)
    {
        year = y; month = m; day = d;
    }
 
    void show()
    {
        cout << year << ' ' << month << ' ' << day << endl;
    }
};
 
class Goods
{
protected:
    int pieces;
    string name;
    string productionCountry;
    Time expireDate;
    string unitOfMeasure;
public:
virtual ostream& serialize(ostream& os)=0;
    virtual istream& unserialize(istream& is)=0;
};
 
class OfficeStuff:public Goods
{
public:
    ostream& serialize(ostream& os);
    istream& unserialize(istream& is);
    void show()
    {
        cout << pieces << endl;
        cout << name << endl;
        cout << productionCountry << endl;
        expireDate.show();
        cout << unitOfMeasure << endl;
    }
    void set(int p, string n, string pr, int ty, int tm, int td, string unit)
    {
        pieces = p;
        name = n;
        productionCountry = pr;
        expireDate.set(ty, tm, td);
        unitOfMeasure = unit;
    }
};
 
ostream& OfficeStuff::serialize(ostream& os) 
{
        
        os.write((const char *) &pieces, sizeof(pieces));
        int l = name.length();
        os.write((const char *) &l, sizeof(l));
        os.write(name.c_str(), name.length());
        int P = productionCountry.length();
        os.write((const char *) &P, sizeof(P));
        os.write(productionCountry.c_str(), productionCountry.length());
        
        expireDate.serialize(os);
        
        int U = unitOfMeasure.length();
        os.write((const char *) &U, sizeof(U));
        os.write(unitOfMeasure.c_str(), unitOfMeasure.length());
        return os;
}
 
istream& OfficeStuff::unserialize(istream& is) 
{
    if(is.read((char *) &pieces, sizeof(pieces))) 
    {
        int l;
        is.read((char *) &l, sizeof(l));
        char* n = new char[l];
        is.read(n, l);
        name.assign(n, l);
        delete n;
        is.read((char *) &l, sizeof(l));
        n = new char[l];
        is.read(n, l);
        productionCountry.assign(n,l);
        delete n;
            
        expireDate.unserialize(is);
        
        is.read((char *) &l, sizeof(l));   
        n = new char[l];
        is.read(n, l);
        unitOfMeasure.assign(n,l);
        delete n;
    }
    return is;
};
 
ostream& Time::serialize(ostream& os) 
{
    os.write((const char *) &year, sizeof(year));
    os.write((const char *) &month, sizeof(month));
    os.write((const char *) &day, sizeof(day));
    return os;
}
 
istream& Time::unserialize(istream& is) 
{
    //int l;
    is.read((char *) &year, sizeof(year));
    is.read((char *) &month, sizeof(month));
    is.read((char *) &day, sizeof(day));
 
    return is;
}
 
////////////////////////////////////////////////////////////////////
 
int main()
{
    vector<OfficeStuff> officeStuff;
    OfficeStuff obj1;
    OfficeStuff obj2;
    obj1.set(1, "asdf", "qwer", 2, 3, 4, "zxcv");
    obj2.set(11, "aaasdf", "qqqwer", 22, 33, 44, "zzzxcv");
 
    officeStuff.push_back(obj1);
    officeStuff.push_back(obj2);
 
    for (auto it = officeStuff.begin(), end = officeStuff.end(); it != end; ++it)
    {
        it ->show();
        cout << endl;
    }
    
    ofstream off( "office.txt", std::ios::binary );
    if( off.is_open() )
    {
        for(vector<OfficeStuff>::iterator itr = officeStuff.begin(); itr != officeStuff.end() ; ++itr)
        {
            if (!itr->serialize(off))
                break;
        }
        off.close();
    } 
    else
    {
        printf( "Can't put data in office.txt'\n");
    }
 
    vector<OfficeStuff> v;
 
    ifstream in( "office.txt", std::ios::binary );
    if( in.is_open() )
    {
         OfficeStuff temp;
         while (temp.unserialize(in))
             v.push_back(temp);
         
         in.close();
    } 
    else
    {
        printf( "Can't get data in office.txt'\n");
    }
    
    
    for (auto it = v.begin(), end = v.end(); it != end; ++it)
    {
        it ->show();
        cout << endl;
    }
    
    system("pause");
    return 0;
}