Need clarification about virtual methods & inheritance

[mark]

I have this class:
class Selections {
OSStatus Init();

protected:
CFMutableSetRef selectionObject s;
static void CFASelectionsAp plier(const void* value, void* ctx);
OSType ready;
public:
Selections();
Selections(cons t Selections &obj);
virtual ~Selections();

virtual OSType GetSelectionSco pe();

virtual UInt32 GetSelectCount( SelectionFlag whichFlags);
virtual CFArrayRef GetSelObjects(S electionFlag whichFlags);
UInt32 GetCountOfClass (SelObjectClass theClass);
CFArrayRef GetSelObjectsOf Class(SelObject Class theClass);
virtual UInt32 GetCountOfScope (OSType theScope);
virtual CFArrayRef GetArrayofScope (OSType theScope);

virtual OSStatus MassAddSelObjec ts(CFArrayRef sorArray);
virtual OSStatus AddSelectededOb ject(SelectedOb jectRef soref);
virtual OSStatus MassRemoveSelOb jects(CFArrayRe f sorArray);
virtual OSStatus RemoveSelectedO bject(SelectedO bjectRef soref);
virtual void RemoveAllSelect edObjects(Selec tionFlag whichFlags);
void RemoveSelObject sOfClass(SelObj ectClass theClass);
virtual void RemoveSelObject sOfScope(OSType theScope);
virtual void RemoveAll();
};

and a subclass:

typedef class DirView DirView;

class DVSelections: public Selections {
DirView* view;
OSType dvsReady;
public:
DVSelections(Di rView* theView);
DVSelections(co nst DVSelections &obj);
~DVSelections() ;

OSType GetSelectionSco pe();
DirView* GetView();
};

When I attempt to compile it, the linker complains with this message:
/usr/bin/ld: Undefined symbols:
vtable for DVSelections

I was under the impression if the virtual function is not defined in a
subclass, the parent class's function will be used.
What am I missing?

This is mac OS X, XCode 2.2 with gcc 4.

TIA
Mark

[Ben Pope]

CodeSafe wrote:

Bahhh
if you want to create a pure virtual interface with pure virtual
destructor do
.h file:

class IMyPureVirtualC lass
{
public:
virtual ~IMyPureVirtual Class() = 0;

virtual void SomeInterfaceFu nction() = 0;
//...
};

.cpp file:
IMyPureVirtualC lass::~IMyPureV irtualClass()
{
//empty destructor (declared as pure virtual)
}

I tend to prefer a header only implementation:

public:
virtual ~IMyPureVirtual Class() = 0 {};


Ben Pope
--
I'm not just a number. To many, I'm known as a string...