IUnknown
From Wikipedia, the free encyclopedia
The published COM specification mandates that COM objects must minimally implement the IUnknown interface. This interface 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 IID). If the COM object does not implement that interface, an 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
{
virtual ULONG AddRef(void) = 0;
virtual HRESULT QueryInterface(REFIID riid, void **ppvObject) = 0;
virtual ULONG Release(void) = 0;
};
The IUnknown interface is defined as a GUID with the value of {00000000-0000-0000-C0000-00000000046}.
[edit] Miscellanea
- IUnknown as serves as the base for Core Foundation's CFPlugIn framework
