Information About

Iunknown
  CATEGORIES ABOUT IUNKNOWN
   
object-oriented programming
   
microsoft apis
   
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IUnknown comprises three functions – ''QueryInterface'', ''AddRef'', and ''Release''.
  • QueryInterface is used to obtain a Pointer to another interface, given a GUID that uniquely identifies that interface (commonly known as an '''interface ID''', or '''IID'''). If the COM object does not implement that interface, an E_NOINTERFACE error is returned instead.

  • AddRef is used by clients to indicate that a COM object is being referenced. This is necessary to ensure that a COM object is not disposed prematurely.

  • Release is used by clients to indicate that they have finished using the COM object. An unreferenced COM object may be safely disposed.


interface IUnknown
{
  • ---ppvObject) = 0;

    • virtual ULONG AddRef(void) = 0;

virtual ULONG Release(void) = 0;
};

The IUnknown interface ID is defined as a GUID with the value of {00000000-0000-0000-C000-000000000046}.


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