CUnknown class

[The feature associated with this page, DirectShow, is a legacy feature. It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation. Those features have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use MediaPlayer, IMFMediaEngine and Audio/Video Capture in Media Foundation instead of DirectShow, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

The CUnknown class implements the IUnknown interface. Most Component Object Model (COM) objects in DirectShow derive from CUnknown.

If you implement a COM object, you might want to derive it from CUnknown. Deriving from CUnknown provides a thread-safe implementation, and saves you the trouble of implementing IUnknown.

For a detailed discussion of how to use this base class, see How to Implement IUnknown. What follows is a brief summary:

• Include the DECLARE_IUNKNOWN macro in the public section of your class definition. This macro declares the three methods of the IUnknown interface.
• Override the NonDelegatingQueryInterface method to support interfaces other than IUnknown. Within this method, call the GetInterface function to retrieve interface pointers.
• In your class constructor, invoke the CUnknown constructor method.

Requirements

See also

DirectShow Base Classes