C++ abstract class without pure virtual functions?

Question

I have a base class

class ShapeF { public:     ShapeF();     virtual ~ShapeF();      inline void SetPosition(const Vector2& inPosition) { mPosition.Set(inPosition); }  protected:     Vector2 mPosition; } 

Obviously with some ommitied code, but you get the point. I use this as a template, and with some fun (ommited) enums, a way to determine what kind of shape i'm using

class RotatedRectangleF : public ShapeF { public:     RotatedRectangleF();     virtual ~RotatedRectangleF(); protected:     float mWidth;     float mHeight;     float mRotation; } 

ShapeF does its job with the positioning, and an enum that defines what the type is. It has accessors and mutators, but no methods.

Can I make ShapeF an abstract class, to ensure nobody tries and instantiate an object of type ShapeF?

Normally, this is doable by having a pure virtual function within ShapeF

//ShapeF.h virtual void Collides(const ShapeF& inShape) = 0; 

However, I am currently dealing with collisions in a seperate class. I can move everything over, but i'm wondering if there is a way to make a class abstract.. without the pure virtual functions.

Answer 1

You could declare, and implement, a pure virtual destructor:

class ShapeF { public:     virtual ~ShapeF() = 0;     ... };  ShapeF::~ShapeF() {} 

It's a tiny step from what you already have, and will prevent ShapeF from being instantiated directly. The derived classes won't need to change.

Answer 2

Try using a protected constructor