Re: Interface method vs QueryInterface()

From:
"Alexander Nickolov" <agnickolov@mvps.org>
Newsgroups:
microsoft.public.vc.atl
Date:
Fri, 15 Dec 2006 09:54:08 -0800
Message-ID:
<OjFzFIHIHHA.5104@TK2MSFTNGP06.phx.gbl>
QI for IUnknown and set the proxy blanket on the returned
interface pointer.

--
=====================================
Alexander Nickolov
Microsoft MVP [VC], MCSD
email: agnickolov@mvps.org
MVP VC FAQ: http://www.mvps.org/vcfaq
=====================================

"H Xia" <huayang.xia@gmail.com> wrote in message
news:1166116286.444885.219680@79g2000cws.googlegroups.com...

What's difference between normal interface method and QueryInterface
method?

In client side, I created an instance by calling:

  MULTI_QI qi = {&IID_ITestCP, NULL, S_OK};
  HRESULT hResult = ::CoCreateInstanceEx( CLSID_TestCP
                                        , NULL
                                        , CLSCTX_LOCAL_SERVER |
CLSCTX_REMOTE_SERVER
                                        , &serverInfo
                                        , 1
                                        , &qi
                                        );

It created an instance and returned an interface from the instance.
Then I call the interface method after properly setting its Proxy
blanket, it succeeded. Then I go even further to query another
interface through the gotten interface, it failed.

  hResult = pUnk->BlanketInfo();
//ok
  hResult = pUnk->QueryInterface(IID_IConnectionPointContainer,
(void**)&pCPC); // access denied

My question is if the second call failed with access denied, why not
the first one?

Thanks in advance.

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