Re: Aggregation in COM

From:

"Igor Tandetnik" <itandetnik@mvps.org>

Newsgroups:

microsoft.public.vc.atl

Date:

Fri, 8 Jun 2007 11:59:14 -0400

Message-ID:

<OqwB3XeqHHA.3456@TK2MSFTNGP02.phx.gbl>

sweetchuck74@gmail.com wrote:

I am trying to create a new component out of existng COM component.
In other words, create outer component with two or more inner
component.
In such case, how should i merge queryInterface function?

For example, I have a component A which has an interface IA, and
component B with an interface IB.
I am creating component C exposing IC interface along with inner
component A and B.

I can implement queryinterface of component C to delegate for IA or IB
request by calling queryinterface on component A or B.
But, after clinent receives IA or IB pointer, how can they go back to
IC interface as in normal COM interface query mechanism?

Read about COM aggregation:

http://msdn2.microsoft.com/en-us/library/ms686558.aspx

See also COMMAP sample - it shows how to implement aggregation, among
other things, in ATL.
--
With best wishes,
Igor Tandetnik

With sufficient thrust, pigs fly just fine. However, this is not
necessarily a good idea. It is hard to be sure where they are going to
land, and it could be dangerous sitting under them as they fly
overhead. -- RFC 1925