creating-an-aggregated-object.md

title	ms.custom	ms.date	ms.reviewer	ms.suite	ms.technology	ms.tgt_pltfrm	ms.topic	dev_langs	helpviewer_keywords	ms.assetid	caps.latest.revision	author	ms.author	manager
Creating an Aggregated Object | Microsoft Docs		11/04/2016			cpp-windows		article	C++	aggregation [C++], creating aggregated objects aggregate objects [C++], creating	fc29d7aa-fd53-4276-9c2f-37379f71b179	10	mikeblome	mblome	ghogen

Creating an Aggregated Object

Aggregation delegates IUnknown calls, providing a pointer to the outer object's IUnknown to the inner object.

To create an aggregated object

1. Add an IUnknown pointer to your class object and initialize it to NULL in the constructor.

2. Override FinalConstruct to create the aggregate.

3. Use the IUnknown pointer, defined in Step 1, as the second parameter for the COM_INTERFACE_ENTRY_AGGREGATE macros.

4. Override FinalRelease to release the IUnknown pointer.

Note

If you use and release an interface from the aggregated object during FinalConstruct, you should add the DECLARE_PROTECT_FINAL_CONSTRUCT macro to the definition of your class object.

See Also

Fundamentals of ATL COM Objects