Re: Interface method vs QueryInterface()

From:

"Alexander Nickolov" <agnickolov@mvps.org>

Newsgroups:

microsoft.public.vc.atl

Date:

Tue, 19 Dec 2006 16:00:19 -0800

Message-ID:

<OuEJXn8IHHA.4384@TK2MSFTNGP03.phx.gbl>

IUnknown is special in that it sets the blanket for all
remote IUnknown methods. These are not covered when
setting the blanket for any other interface because IUnknown
is really implemented locally. It calls the remote IUnknown
via IRemUnknown internally when necessary, but that's
invisible to the caller.

--
=====================================
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:1166543122.483859.317530@i12g2000cwa.googlegroups.com...

It works. Thank you.

I don't understand why:

1). With the interface I got by CoCreateInstanceEx, I can call the
interface method; but not QueryInterface method (for any interface)?
Why I have to start from IUnknown?
2). For each interface I have to set proxy blanket to query other
interface, but this time I don't have to start from IUnknown.

On Dec 15, 12:54 pm, "Alexander Nickolov" <agnicko...@mvps.org> wrote:

QI for IUnknown and set the proxy blanket on the returned
interface pointer.

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

"H Xia" <huayang....@gmail.com> wrote in
messagenews: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.