Re: Why does it do that? - COM Discussion Boards

19-Mar-02 12:50

Hi all,

In my server implementation, I have the following code:

// Create a new CComEnum<> of IUser* interfaces
typedef CComObject< CComEnum<ienumuser, &iid_ienumuser,=""
="" iuser*,="" _copyinterface<iuser=""> > > EnumUser;
EnumUser* pNewEnum = NULL;
EnumUser::CreateInstance(&pNewEnum); // This is the line with error

However, when I tried to compile my server, I receive the following:

error C2259: 'CComObject<class atl::ccomenum<struct="" ienumuser,&struct="" _guid="" const="" iid_ienumuser,struct="" iuser="" *,class="" atl::_copyinterface<struct="">,class ATL::CComSingleT
hreadModel> >' : cannot instantiate abstract class due to following members:

c:\program files\microsoft visual studio\vc98\atl\include\atlcom.h(4403) : while compiling class-template member function 'long __stdcall ATL::CComObject<class atl::ccomenum<struct="" ienumuser,&struct="" _guid="" const="" iid_ienumuser,struct="" iuser="" *,
class="" atl::_copyinterface<struct="">,class ATL::CComSingleThreadModel> >::CreateInstance(class ATL::CComObject<class atl::ccomenum<struct="" ienumuser,&struct="" _guid="" const="" iid_ienumuser,struct="" iuser="" *,class="" atl::_copyinterface<struct="">,class AT
L::CComSingleThreadModel> > ** )'

I have IEnumUser declared in the server idl file, and IUser declared in a separate dll.

Does anyone know what I have done wrong? Your help is much apprepriated.

Sunny

Problem with CComEnum

Sunny_leung19-Mar-02 12:53

19-Mar-02 12:53

Sorry, the error message got cutoff. It should be:

error C2259: 'CComObject<class atl::ccomenum<struct="" ienumuser,&struct="" _guid="" const="" iid_ienumuser,struct="" iuser="" *,class=""
atl::_copyinterface<struct="">,class ATL::CComSingleT
hreadModel> >' : cannot instantiate abstract class due to following
members:

c:\program files\microsoft visual studio\vc98\atl\include\atlcom.h
(4403) : while compiling class-template member function 'long __stdcall
ATL::CComObject<class atl::ccomenum<struct="" ienumuser,&struct="" _guid=""
const="" iid_ienumuser,struct="" iuser="" *,
class="" atl::_copyinterface<struct="">,class
ATL::CComSingleThreadModel> >::CreateInstance(class
ATL::CComObject<class atl::ccomenum<struct="" ienumuser,&struct="" _guid=""
const="" iid_ienumuser,struct="" iuser="" *,class="" atl::_copyinterface<struct=""
iuser="">,class ATL::CComSingleThreadModel> > ** )'

Why does it do that?

#realJSOP19-Mar-02 7:43

#realJSOP

19-Mar-02 7:43

I call CoInitialize(NULL) in a DLL, and after some processing, I call CoUnitialize in the same DLL. This causes the app using the DLL to crash (rather spectacularly) in another un-related part of the code.

"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001

Carlos Antollini19-Mar-02 8:13

Carlos Antollini

19-Mar-02 8:13

When that ocurss I prefer to use the CoInitialize and the CoUnitialize out of the DLL, before and after to call the function into the dll

Best Regards

Carlos Antollini.
Sonork ID 100.10529 cantollini

#realJSOP19-Mar-02 8:48

#realJSOP

19-Mar-02 8:48

I tried moving the CoInit/CoUninit to the class in the app that actually uses the DLL.

COM has to be available the entire time that the DLL lives in the program space because I have interfaces that might persist between calls to the DLL's functions.

There is truly strange stuff happening.

It might even be better if I called CoInit in OnInitInstance in the app instead.

"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001

David Salter19-Mar-02 10:56

David Salter

19-Mar-02 10:56

Isn't it recommended to call CoInitializeEx(). I have had problems with CoInitialise() before and changing to ...Ex may help.

Dave.

Sunny_leung19-Mar-02 12:49

Trying to get an element from SAFEARRAY

19-Mar-02 12:49

Did you freed all the interface references?
E.g. YourInterface->Release(), or if you are using smart pointers, setting them to NULL?
I have seen a crash before when I forgot to free all the references before I called CoUninitialize().

Hope it helps,

Sunny

Sunny_leung18-Mar-02 14:07

Re: Trying to get an element from SAFEARRAY

18-Mar-02 14:07

Hi,

I have stumbled across a problem again, and this time, it is on retrieving an element from a SAFEARRAY. The following code shows what I am trying to achieve:

// Creates a user
IUser* pUser4 = NULL;
CoCreateInstance( __uuidof( User ), NULL, CLSCTX_INPROC_SERVER,
IID_IUser, (void**)&pUser4 );

// Store my first name into it
pUser4->put_FirstName( L"Sunny" );

// Creates a variant that contains an array of type IUnknown pointers
_variant_t* userArray = new _variant_t;
userArray->vt = VT_ARRAY | VT_UNKNOWN;

// Create the array
SAFEARRAY* pSA;
SAFEARRAYBOUND bounds = { 1, 0 };
pSA = SafeArrayCreate( VT_UNKNOWN, 1, &bounds );

// Turn my pUser4 pointer into the IUnknown pointer
IUnknown* pUnk = NULL;
pUser4->QueryInterface( IID_IUnknown, (void**)&pUnk );

// put the IUnknown pointer into the array, and store the array
// into the variant
long a = 0;
SafeArrayPutElement( pSA, &a, pUnk );
userArray->parray = pSA;

// Retrieve the element
SAFEARRAY* ans = userArray->parray;
IUnknown* pUnk2 = NULL;
SafeArrayGetElement( ans, &a, pUnk2 ); // problem occurs
IUser* pUser5 = NULL;
pUnk2->QueryInterface( IID_IUser, (void**)&pUser5 );

BSTR first;
pUser5->get_FirstName( &first );

//======================== END

The problem arises when I tried to get the IUnknown pointer from the array by calling SafeArrayGetElement. I looked at the debugger, and it showed that the address of pUnk2 is 0x00000000.

I am wondering if anybody known what I have done wrong?
Help is apprepriated Smile | :)

Sunny

Mazdak18-Mar-02 20:58

Mazdak

18-Mar-02 20:58

I'm not sure the problem is that but I know if you want to access the buffer of SAFEARRAY,after you create it you have to use SafeArrayAccessData() method,and after you finished working with it you have to
use SafeArrayUnAccessData().

Mazy

"So,so you think you can tell,
Heaven from Hell,
Blue skies from pain,...
How I wish,how I wish you were here."
Wish You Were Here-Pink Floyd-1975

In-place activation of Excel

18-Mar-02 2:17

Hi,

I'm using ::OleCreate to activate an Excel worksheet (Excel.Sheet) in-place in an MDI child window. The problem is I want to control the out-of-process server instance (Excel.Application) that is instancing the worksheets.

The default Windows behviour seems to either create the Excel.Sheet instances from whichever server was launched first, or just creates a new server if no server is activated.

Does anyone know of a way of specifying which server the out-of-process object is created in?

Many thanks in advance.

ActiveX instanciation in VB

Jerome Conus18-Mar-02 0:40

Jerome Conus

18-Mar-02 0:40

Hi !

I'm building an App using Visual Basic 6, where I would like to display many ActiveX controls.

The number and types of ActiveX to display is not hard-coded in the App, but rather put in a text file that would be read during initialization of the App, thus allowing me to add/remove ActiveX controls without recompiling my App.

My problem is I don't know how to use an ActiveX control in VB without registering it (Project->Component) and putting it into a form. I would like to register it during code execution and placing it into my form dynamically.

Anyone knows how to do that ?

Thank you for your help !

Jerome

Re: ActiveX instanciation in VB

Joao Vaz18-Mar-02 1:16

Joao Vaz

18-Mar-02 1:16

Jerome C wrote:
I would like to register it during code execution and placing it into my form dynamically

Confused | :confused:

First , normally, you must always register the COM object.
Second you're are talking perhaps about late binding ...
So you can declare something like this:

dim x as object
'read file, retrieve the progid of the class

set x = CoGetObject("",progid)
or
'read the name of class to instancing
set x = CreateObject("myClass.xpto")

If you want really to register you must deal with reg* api , like RegSaveKey or RegSetValue ..., for instance placing all the registries entries on the text file per object and using the registry keys to save the values ..., or writing a reg file for each object and call the ShellExecute api to automatically merge the .reg file, and so on ... you get the idea ...

Cheers,

Joao Vaz

STG_E_MEDIUMFULL When Saving an Image to Stream

Serge Baltic17-Mar-02 23:26

Serge Baltic

17-Mar-02 23:26

What does that error (STG_E_MEDIUMFULL) mean?

The message is 'Not enough storage is available to complete this operation.' still it has nothing in common at all with the real problem. What can cause such a message and how to fix it up?

The code is (error-handling omitted):

StgCreateDocfile(L"Image.bmp", STGM_CREATE | STGM_READWRITE | /*STGM_DELETEONRELEASE | */STGM_SHARE_EXCLUSIVE, 0, &pStorage);

pStorage->CreateStream(L"Image.bmp", STGM_CREATE | STGM_READWRITE | STGM_SHARE_EXCLUSIVE, NULL, NULL, &pStream);

Image->QueryInterface(IID_IPersistStream, (void**)&pPersistStream);

OleSaveToStream(pPersistStream, pStream);

* Origin: Silence Must Be Heard (2:5030/744.235)

Can I control the IE browser by using a COM?

wabc17-Mar-02 18:47

wabc

17-Mar-02 18:47

Can I control the IE browser by using a COM?

is there a example?

thanks!

pba_18-Mar-02 4:17

pba_

18-Mar-02 4:17

Check MSDN / Platform SDK / Web development / Internet SDK / Reusing browser technology.

David Salter19-Mar-02 10:53

David Salter

19-Mar-02 10:53

Yes,

From memory you need to connect to "InternetExplorer.Application". Check out the OLE/COM viewwer and it will show you all the methods/property you can access.

Dave.

wabc19-Mar-02 15:10

wabc

19-Mar-02 15:10

Thank you for your help!

I want get the data that IE browser send to the server before the sending action is executed,encrypt the data,and then give the crypto-data to the browser for sending to the server!

Could you give me some advice about that!