pure virtual functions in a DLL

ok... first, let me say that I was playing with pure virtual functions, and got it to work all in one app. This is how I did, it really:

in TheClass.h (example):

Code:

---

class CMyClass
{
    public:
          CMyClass();
 

      virtual void Initialize() = 0;
};

---

in TheClass.cpp:

Code:

---

#include "TheClass.h"

CMyClass::CMyClass()
{
    Initialize();
}

---

in Main.cpp:

Code:

---

#include "TheClass.h"
class MyClass2 : public CMyClass
{
  public:
    void Initialize()
    {
      cout << "YAY!" << endl;
    }
}

int main()
{
  MyClass2  Blah;

  //some random code

  return 0;
}

---

That worked all in one app, just fine. So, while expirementing with it, I figured it'd be useful if I could put TheClass.h and TheClass.cpp into a DLL. The compiling worked great, but then linking came, and it said along the lines of:

Quote:

---

error LNK2019: unresolved external symbol "public: virtual void __thiscall CMyClass::Initialize(void)"referenced in function "public: __thiscall CMyClass::CMyClass(void)"

---

So, my question is, is there any way that I can seperate it into a DLL like that? I tried taking off the "= 0" and doing just a "{ cout << "ok" << endl; }" thing, and that worked great, but then the new function created in the app was never called.

I guess it's fine if it can't be done, but I figured I'd see if someone knows a way anyway... I guess I'm just figuring mabye it's possible, and then I can make use of it. :)

Thanks!

Ok, someone just gave me a tip that it doesn't work when in the constructor and destructor... with some playing around, I found that my problem was exactly that. Looking back over the code I had used previously, I now recall I didn't use a constructor or destructor, but that didn't really phase me until someone brought up to me that it couldn't be done that way.

Sorry. :rolleyes:

Quote:

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Originally Posted by crazycheetah

guess it's fine if it can't be done, but I figured I'd see if someone knows a way anyway... I guess I'm just figuring mabye it's possible, and then I can make use of it. :)

---

Well... what would be the point of having a pure virtual function in a DLL? A DLL is meant to provide an implementation - code which can be linked at run time and executed. The whole point about a pure virtual function, in contrast, is that it has no implementation - it represents just an interface for an implementation to be provided elsewhere. So a "pure virtual function in a DLL" is just something that doesn't make any sense.

If you want to create CMyCalss in your app you should exprot CMyClass from dll.
There is another way just like COM's methord.