IUnknown::QueryInterface method

Article
06/06/2016

Note This topic describes IUnknown in the context of the AVIFile and AVIStream interfaces. For general information about IUnknown, see the Component Object Model (COM) documentation in the Windows SDK.

The QueryInterface method determines if an interface can be used with an object. Used by the following interfaces: IAVIEditStream, IAVIFile, IAVIStream, IAVIStreaming, and IGetFrame.

Syntax

HRESULT QueryInterface(
         LPUNKNOWN ps,
   const IID       riid,
         void      **ppvObj
);

Parameters

ps
Pointer to an IAVIEditStream, IAVIFile, IAVIStream, IAVIStreaming, or IGetFrame interface.
riid
Identifier of the interface being queried.
ppvObj
Pointer to a buffer that receives a pointer to the object whose interface is queried or NULL when an interface is not supported.

Return value

Returns a pointer to the current interface if successful or E_NOINTERFACE otherwise.

Remarks

For handlers written in C++, QueryInterface has the following syntax:

HRESULT QueryInterface(const IID &riid, void **ppvObj);

Requirements

Minimum supported client	Windows 2000 Professional [desktop apps \| Windows Store apps]
Minimum supported server	Windows 2000 Server [desktop apps \| Windows Store apps]
Header	Unknwn.h

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