Hi all, I thought I understood the ideas behind inheritance and such like, but some simple code I am trying to compile with VC++ 2005 Express is giving me link errors. The code is as follows:- In one file, ACEntity.h, I have a pure abstract class.

#ifndef ACENTITY_H
#define ACENTITY_H

#include <string>

class ACEntity
{
public:
	std::string sID;

	ACEntity();
	virtual ~ACEntity();

};

#endif

In another, ACSpace.h, I have an abstract class that inherits from ACEntity.

#ifndef ACSPACE_H
#define ACSPACE_H

#include "ACEntity.h"

class ACSpace : public ACEntity
{
public:
	ACSpace();
	virtual ~ACSpace();

	virtual void AcceptEntityEntrance( ACEntity *e)=0;
	virtual void AcceptEntityExit( ACEntity *e)=0;
};

#endif

I then have a concrete class that inherits from ACSpace. The header for this is.

#ifndef CAREA_H
#define CAREA_H

#include "ACSpace.h"

class ACEntity;

class CArea : public ACSpace
{
public:
	float m_flHeight, m_flWidth;

	CArea(float t_flWidth, float t_flHeight); 
	virtual ~CArea();

	void AcceptEntityEntrance( ACEntity *e) {};
	void AcceptEntityExit( ACEntity *e) {};

};

#endif

and the implementation so far is.

#include "CArea.h"

CArea::CArea(float t_flWidth, float t_flHeight)
{
	m_flWidth = t_flWidth;
	m_flHeight = t_flHeight;
}

When I try to compile this, I get the following error.

CArea.obj : error LNK2019: unresolved external symbol "public: virtual __thiscall CArea::~CArea(void)" (??1CArea@@UAE@XZ) referenced in function "public: virtual void * __thiscall CArea::`scalar deleting destructor'(unsigned int)" (??_GCArea@@UAEPAXI@Z)

Can someone please explain what I'm doing wrong here, because as far as I can see, what I have should compile? Thanks in advance, Wibbs

You simply didn't implement CArea::~CArea()...
You'll probably want to implement ACEntity's constructor and destructor too. Also there's nothing abstract about it, it doesn't have a single pure virtual member?
edit: I shouldn't do random things while typing answers heheh

Thanks for all the quick responses, problem solved :)