Making a class generate another class? - c++

Question

Okay, so I have an assignment for a class that requires us to use a series of classes together, to simulate a police officer issuing a ticket.
Here's how it works:
ParkedCar class:
To know the cars make, model, color, license number, and the number of minutes
that the car has been parked
ParkingMeter Class:
know how much time has been purchased
ParkingTicket Class:
know make, model, color, license of the car, calculate the fine, as well as the name and badge number of the officer issuing the ticket
PoliceOfficer Class:
Know the name a badge number of the officer
AND
Examine ParkedCar and ParkingMeter objects and determine if a ticket is needed, if so, generate a ParkingTicket object.
Here's what code I have so far:
#include<iostream>
#include<cstdlib>
#include<cstring>
#include<ctime>
using namespace std;
class ParkedCar
{
string sMake;
string sModel;
string sColor;
string sPlate;
int iMinsParked;
public:
ParkedCar();
string getMake() const
{ return sMake; }
void setMake(string temp)
{ sMake = temp; }
string getModel() const
{ return sModel; }
void setModel(string temp)
{ sModel = temp; }
string getColor() const
{ return sColor; }
void setColor(string temp)
{ sColor = temp; }
string getPlate() const
{ return sPlate; }
void setPlate(string temp)
{ sPlate = temp; }
int getMins() const
{ return iMinsParked; }
};
ParkedCar::ParkedCar()
{
srand(time(NULL));
iMinsParked = (rand() % 10000);
}
class ParkingMeter
{
int iMinsPurch;
public:
void setMins(int temp)
{ iMinsPurch = temp; }
int getMins() const
{ return iMinsPurch; }
}
class Ticket : public ParkedCar
{
public:
string getName()
{ return sName; }
int getBadge()
{ return iBadge; }
};
class Officer
{
string sName;
int iBadge;
public:
friend string Ticket::getName();
//{ return sName; }
friend int Ticket::getBadge();
//{ return iBadge; }
};
int main()
{
ParkedCar Park;
cout << endl << endl;
cout << Park.getMins();
cout << endl << endl;
return 0;
}
Where I'm confused is mostly on the Ticket and Officer classes. The assignment clearly wants Ticket to have it's own information from all the other classes, but I'm not sure how to pass that information along. I've tried making it a child class of ParkedCar, but I just get a multiple definitions error. And I can't get the friend functions to work. I've tried them both ways and if I make them within Ticket, it tells me Officer isn't defined. And I'm really confused on how I'm supposed to write code for Officer generating an instance of Ticket when nothing has actually been initialized yet.
So:
How do I get all the information into the Ticket class?
How would I get Officer to generate an instance of Ticket?
Please keep in mind this is a STUDENT assignment, not something professional. I just want to do what the assignment says. I'm not interested in ways "around" the problem, because that's not what the prof wants.
Thanks in advance for your time. :D

Answer 1

Firstly: learn to use constructors. All this stuff you're setting...it is integral to the identity of a car, or a cop, etc. It should have been provided when the object was built. C++ isn't Java; quit treating classes like Java beans. :P
Secondly, a Ticket is not a ParkedCar. It associates with a car, but is not one itself. Consider instead:
class Ticket {
ParkedCar violator;
Officer issuer;
public:
Ticket(const Officer &cop, const ParkedCar &car) :
violator(car), issuer(cop) {
}
ParkedCar getCar() { return violator; }
Officer getOfficer() { return issuer; }
// Note, no mutators here!
// The biggest reason you had to have mutators, is that your construction
// was incomplete.
// The info associated with a Ticket should not be modified once the ticket
// is written. And since the constructor has all the info needed, there's no
// need to provide a way to modify them.
};
So an Officer doesn't need to know about the potentially-intricate details of a car, or exactly what info a Ticket needs. He can just hand himself and the car over to the constructor, and trust that it will extract whatever info it needs. (In this case, we just store copies of both items.)
class Officer {
std::string name;
int badge_number;
public:
Officer(const std::string& name, int badge) : name(name), badge_number(badge) { }
public std::string getName() { return name; }
public int getBadgeNumber() { return badge_number; }
Ticket writeTicketFor(const ParkedCar &violator) {
return Ticket(*this, violator);
}
};