CODEWITHSUNDEEP
c++inheritance
Tarta
Tarta

Reputation: 2063

Accessing a specific method of an inherited class in C++

I come from Java background and I have the following little scenario that doesn't fit my understanding:

template<typename T>
class GeomObject{
  public:
    T position;

    virtual Vec3<T> getPosition() = 0;
}


template<typename T>
class Plane : public GeomObject<T> {
  public:
    Vec3<T> position;
    T range;

    Vec3<T> getPosition() { return position; }
    T getRange() { return range;}
}

In my main:

vector<GeomObject<float>*> g_objects;
g_objects.push_back(new Plane<float>());

g_objects[0]->getRange(); //ERROR

I cannot access the getRange() method somehow. This was possible in Java but here is not, not even by casting (Sphere)g_objects[0]->getRange(); I would like tho, to keep the vector as a vector of GeomObjects . Is there something I am doing wrong?

Upvotes: 1

Views: 64

Answers (1)

Sander De Dycker
Sander De Dycker

Reputation: 16243

The getRange member function isn't part of the GeomObject definition, so you cannot call it through a pointer to GeomObject.

Try adding this in GeomObject :

virtual T getRange() = 0;

From further comments, it's made clear that getRange is specific to a Plane, so it cannot be added as a (pure) virtual member function in GeomObject.

In that case, you can still access Plane::getRange, but you'll have to downcast the pointer first. Eg. using dynamic_cast :

dynamic_cast<Plane<float>*>(g_objects[0])->getRange();

(omitting error checks for brevity).

Having to resort to this, is usually a code smell though. Ie. it's a sign that your design could be improved.

Upvotes: 7

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