external unresolved symbol

Hi,

Can someone explain what does this error means?

Webcam error LNK2001: unresolved external symbol "protected: long __thiscall CCaptureVideo::OnGraphNotify(unsigned int,long)" (?OnGraphNotify@CCaptureVideo@@IAEJIJ@Z)

Thanks a lot in advance!

It usually means you haven't linked to whatever library or object that contains the function mentioned in the error. It may alternatively be that you've not provided a definition for the function in question. Read your compiler documentation on how to properly link the required library; checking out the error code should also provide useful information, too.

Is CCaptureVideo your code or library code?

a code i am learning. It is not a library.

**added**

i should elaborate more.

so i have a header file:

Code:

---


#define WM_GRAPHNOTIFY WM_USER+1

class CCaptureVideo : public CWnd
{
    protected: afx_msg HRESULT OnGraphNotify(WPARAM wp, LPARAM lp);
    DECLARE_MESSAGE_MAP()
};

---

Then in my .cpp file:

i have the constructer, the destroyer then have:

Code:

---


BEGIN_MESSAGE_MAP(CCaptureVideo, CWnd)
    ON_MESSAGE(WM_GRAPHNOTIFY, OnGraphNotify)
END_MESSAGE_MAP()

---

so when i compile, the error mentioned in my first post occurs. if i comment the ON_MESSAGE line.. the compilation runs fine. This should help you guys explain to me more.. :)

You should provide a body for the function OnGraphNotify
that will be called on when the message WM_GRAPHNOTIFY occurs

ahh yes you are right. i did not have my function implementation codes. I just saw an example the moment you posted.

Thanks a lot anyway.

Cheers to all that replied.