Re: BSTR release - COM Discussion Boards

Re: Interface as Events parameter and it release

30-Mar-04 2:59

Hi all

Suppose i create COM object with event what use interface as parameter.

CATLWrappedClass<...>{

Fire_MyEvent(ISomeInterface* pIface)
{
...
}

}

Now from elsewhere i arise this event

...

//This routine query interface from internal object and add
//referience number of one
ISomeInterface* pIface = GetSomeIface();

Fire_MyEvent(pIface);

//My question is - "should client release this interface
//or this my labour?"

pIface->Release();//Do i???

Thanks

Anonymous30-Mar-04 8:42

Anonymous

30-Mar-04 8:42

No you shouldn't
The caller controls (allocates and frees) all [in] parameters.
[out] parameters allocated by callee and been freed by caller
Edward

Re: Interface as Events parameter and it release

Vi231-Mar-04 1:22

Vi2

31-Mar-04 1:22

real_space_monkey wrote:
//This routine query interface from internal object and add referience number of one
ISomeInterface* pIface = GetSomeIface();

Fire_MyEvent(pIface);

//My question is - "should client release this interface or this my labour?"

pIface->Release();//Do i???

YES, you should, because the pIface is in your ownership.

With best wishes,
Vita

Data Bound ActiveX control

Dimitris Vasiliadis29-Mar-04 23:29

Dimitris Vasiliadis

29-Mar-04 23:29

I am trying to create an ActiveX control to be used within MS Access. I want to bind it in a field within an Access form, like you can do with the objects access provides.

Is this possible?
Does anyone have an idea what interfaces should I implement?

Thanks in advance for any hints.

...Plug & Pray... Dead | X|

Help: catch/handle window messages in COM dll

usouthal29-Mar-04 13:19

usouthal

29-Mar-04 13:19

I need to catch and handle the WM_DEVICECHANGE message in my COM dll server. I tried to force one of the class inherit from CWindowImp, but it doesn't work. Any idea? Thanks.

Linn

BSTR release

El'Cachubrey28-Mar-04 21:14

28-Mar-04 21:14

Hi all
I use in my COM interafse some method which receive BSTR as parameter ie

HRESULT MyObject::SomeFun(BSTR str)
{

SysFreeString(str);//exception is here

}

And i invoke this method from VB client

As far as is known i should free BSTR what had been created by myself directly with SysFreeString(...)
and in my example i free it in this way.But i had unhandled exception at my VB client during SysFreeString(str)

Thats wrong???
Thanks all

Rory Solley28-Mar-04 22:18

Rory Solley

28-Mar-04 22:18

The object that creates the string should be responsible for freeing it again. In your case, whoever calls SomeFun() will create the string (say by SysAllocString) and will also be responsible for calling SysFreeString on the object they created as a parameter, once the call returns:

BSTR bstrNewString = ::SysAllocString(L"Test");
pIMyObjectPtr->SomeFun(bstrNewString);
::SysFreeString(bstrNewString);

El'Cachubrey29-Mar-04 0:27

29-Mar-04 0:27

THANK

Jörgen Sigvardsson29-Mar-04 3:38

Jörgen Sigvardsson

29-Mar-04 3:38

The rules are:
[in] data initialized before passed to method, and is expected to be initialized when the method returns. COM-objects living in the same apartment can modify parameters (i.e. strings) eventhough they're labeled as [in]. It may or may not work - it sure won't work across apartment boundaries.

[out] has no reference to any valid data. If it does, that's just a coincidence - don't rely on it. You, the method callee, are responsible for allocating data to return through this parameter (or nothing/NULL if you're dealing with reference semantics).

[in, out] If you are to update the value of such a parameter, you must first free the passed in value, and allocate a new one for the return. Note that if [in, out] long* param is passed, you don't have to allocate memory, just *param = value;. If you get a [in, out] IInterface** p, then (*p)->Release(); *p = ....

[edit][out, retval] has the exact semantics as a [out]. Clients such as VB uses the retval attribute only to synthesize a return type for methods.[/edit]

--
Din mamma.

El'Cachubrey30-Mar-04 0:38

30-Mar-04 0:38

THAKS ALL

Anonymous15-Apr-04 2:36

Anonymous

15-Apr-04 2:36

Tapi3 COM

babur_rizwan28-Mar-04 12:56

babur_rizwan

28-Mar-04 12:56

please tell me how can i initialize ITBasicCallControl
interface of tapi3lib.dll component in VC.net using type library

thanx....

babur

Outlook Express add-in

dorutzu28-Mar-04 9:17

dorutzu

28-Mar-04 9:17

Hi gurus,

I'm working on a ATL plug-in for MS Outlook, but I would like to make it work on Outlook Express as well. I understand that it's not possilble via COM technology (as OE does not expose any COM interfaces Sigh | :sigh:

), but something with hooks? Any documentation on the subject?
Any help / hint would be much appreciated.

Thanks in advance,
Doru K.

Stephane Rodriguez.28-Mar-04 9:51

Stephane Rodriguez.

28-Mar-04 9:51

There are articles here on codeproject. The guy is Amit Dey.

dorutzu28-Mar-04 10:04

dorutzu

28-Mar-04 10:04

Hi,

I only found his article about Outlook add-ins, but Outlook Express is a COMPLETELLY different thing. Maybe there is an article about Outlook Express as well, but I didn't find it...could you send me the link?

Thanks,
Doru

FearlessBurner30-Mar-04 1:41

FearlessBurner

30-Mar-04 1:41

I recently used the interface that I found in this article
http://www.codeproject.com/useritems/email.asp?target=MAPI[^]

Some of the code is perhaps a bit rusty, and may not be fully implemented, but working with the example code made it easy for me to understand the mechanisms involved, and it was straightforward to sort out any problems and adapt the COM interface for my own needs. I was extremely grateful for the help provided by this article.