Question

So this is a small part of a large assignment I have, I’m just unsure of the syntax for this.

I have a base class named Vehicle, which has these members: int fuelAmt and int fuelUsage)

(I am using namespace std)

I overloaded the << operator this way:

ostream& operator<<(ostream& osObject, const Vehicle& myVehicle)
{
    cout << "Fuel Usage Rate: " << myVehicle.fuelUsage << endl
         << "Fuel Amount:     " << myVehicle.fuelAmt << endl;

    return osObject;
}

I then call it this way:

cout << Vehicle;

The result is (example):

Fuel Usage Rate: 10;
Fuel Amount: 50;

---

I also have an Airplane class which derives from the Vehicle class, it introduces a new member: int numEngines.

How can I overload the << operator in the Airplane class, so that it will first call the “Vehicle overloaded operator results”, and then the results of whatever I tell the << operator to print from the derived class… So, here’s what I mean:

I need it to function like this in the Airplane class:

ostream& operator<<(ostream& osObject, const Airplane& myAirplane)
{
        //First print the Fuel Usage rate and Fuel amount by calling
        //the Base class overloaded << function

         //then
        cout << "Number of Engines: " << myAirplane.numEngines << endl;

    return osObject;
}

How do I trigger the base class execution of outputting its members’ values, in this derived class?

Is it something like changing the header? Like this:

ostream& operator<<(ostream& osObject, const Airplane& myAirplane): operator<<Vehicle

Answer 1

How about the following:

ostream& operator<<(ostream& osObject, const Airplane& myAirplane)
{
    osObject << static_cast<const Vehicle &>(myAirplane);
    osObject << "Number of Engines: " << myAirplane.numEngines << endl;

    return osObject;
}