RAD Studio VCL Reference
TComponent.QueryInterface Method

Returns a reference to a specified interface if the object supports that interface.

function QueryInterface(const IID: TGUID; out Obj): HResult; virtual; stdcall;
virtual __fastcall __stdcall HRESULT QueryInterface(const TGUID IID,  Obj);

QueryInterface checks whether the component supports the interface specified by IID, and if so, returns a reference to that interface as the Obj parameter. If the component does not support the interface, the Obj parameter returns nil (Delphi) or NULL (C++).

Note: For components that act as COM object wrapper, QueryInterface calls the QueryInterface method of the internal COM object.

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