COM Discussion Boards

HOWTO: Pass VB string into VC++ created ATL Object?

Tim Rymer11-Oct-01 10:31

11-Oct-01 10:31

I'm having trouble getting VB to pass in a String into a ATL Object created with VC++ 6.0 -- I dont use MFC. Please help if ya' can! all i really need to know is how to pass in/return... I found some MSDN articles, but they werent using an ATL object. Thanks in advance...

SHABBA!!

Re: HOWTO: Pass VB string into VC++ created ATL Object?

C^hris L^osinger11-Oct-01 10:33

C^hris L^osinger

11-Oct-01 10:33

if the string is input only, use "BSTR". if you need to change the string (output), use "BSTR *".

there are non-MFC classes that can help with BSTR manipulation, such as "bstr_t" and "CComBSTR".

a BSTR is COM's preferred string pasing method.

-c

------------------------------
Smaller Animals Software, Inc.
http://www.smalleranimals.com

COM client structure

Peter Molnar11-Oct-01 8:29

Peter Molnar

11-Oct-01 8:29

Sirs,

this is my first COM adventure so I need your advise.
I have an in process server with lots of interfaces and even more methods in it.
The manufacturer of the dll provides a sample code snippet of how to get pointers to all the interfaces:

//First object
HRESULT hr = ::CoCreateInstance(... 
if ( !FAILED( hr ) ) {

   //First interface
   hr = pIUnknown->QueryInterface(... 
   if ( !FAILED( hr ) ) {
        
      //Second interface
      hr = pIUnknown->QueryInterface(...
      if ( !FAILED( hr ) ) {

         //Third interface
         hr = pIUnknown->QueryInterface(...
         if ( !FAILED( hr ) ) {
            ...
            //Here comes the code that uses the interfaces
            ...
         } else {
            ...//Third interface failed
         }
      } else {
         ...//Second interface failed
      }
   } else {
      ...//First interface failed
   }
} else {
...//CreateInstance failed
}

Why are the QI calls NESTED? I tried putting them after each other but the same code taken from the nested structure didn't work (Runtime library: abnormal program termination) although all interfaces were succesfully created.
I would like to create the appropriate interfaces in my dialogs' OnInitdialogs and release in the OnDestroyWindow. Is that possible? Any sugggestions?

Thanks for your help in advance.

Bunburry

A subject that is beautiful in itself gives no suggestion to the Artist. It lacks imperfection. (O.Wilde)

Re: COM client structure

Amit Dey13-Oct-01 6:21

Amit Dey

13-Oct-01 6:21

The nested QI() calls are probably because the ability to QI a second interface depends on the success or failure of QI() of the first interface.

As to the dialog, OnInitDialog() and OnDestroyWindow() are perfect for creating and releasing COM objects in dialogbased applications.

I'm an alien, I'm an alien
it's a beautiful life....
Bush

Re: COM client structure

Michael Dunn13-Oct-01 7:56

Michael Dunn

13-Oct-01 7:56

I can't tell from your code snippet, but the "Here comes the code that uses the interfaces" part probably uses all three interfaces. Thus all three QIs have to succeed before that code can work.

And BTW it'll be easier to understand if you replace "!FAILED" with "SUCCEEDED" Smile | :)

--Mike--
http://home.inreach.com/mdunn/
"The Earth is doomed." -- Rupert Giles
Heart | [heart]

your

with

and

Where I have to call CoUnInitialize function if I have COM interfaces in (MFC) application main class?

Rula Ghabbiesh11-Oct-01 5:42

Rula Ghabbiesh

11-Oct-01 5:42

I couldn't call CoUnInitialize function in ExitInstance or in class destructor(there will be crash), since I have COM interfaces (member variables)in application main class,(They are smart pointers),so a calling to COM interfaces release function will make the problem.

Re: Where I have to call CoUnInitialize function if I have COM interfaces in (MFC) application main class?

Shadi Al-Kahwaji12-Oct-01 9:05

Shadi Al-Kahwaji

12-Oct-01 9:05

Hi,

If you are using Document/View Architecture, you can put your smart pointers as member variavles in the Document class. At that time you can call CoUnitialize() either in the Main App Destructor or in App ExitInsnance Smile | :)

.

ShadiK

Shadi Al-Kahwaji

Re: Where I have to call CoUnInitialize function if I have COM interfaces in (MFC) application main class?

Michael Dunn12-Oct-01 16:06

Michael Dunn

12-Oct-01 16:06

You don't have to. You call AfxOleInit() in your app's InitInstance() and that's it. MFC handles uninitializing COM when you app closes.

--Mike--
http://home.inreach.com/mdunn/
"The Earth is doomed." -- Rupert Giles
Heart | [heart]

your

with

and

Re: Where I have to call CoUnInitialize function if I have COM interfaces in (MFC) application main class?

Rula Ghabbiesh14-Oct-01 22:00

Rula Ghabbiesh

14-Oct-01 22:00

It doesn't solve my problem. The same crash will happen when the application releases smart pointers members. Smile | :)

Re: Where I have to call CoUnInitialize function if I have COM interfaces in (MFC) application main class?

Michael Dunn14-Oct-01 22:05

Michael Dunn

14-Oct-01 22:05

Then call their Release() methods in your ExitInstance().

--Mike--
http://home.inreach.com/mdunn/
"The Earth is doomed." -- Rupert Giles
Heart | [heart]

your

with

and

Passing a COM interface to an out of process COM object

Jeremy Pullicino11-Oct-01 3:33

Jeremy Pullicino

11-Oct-01 3:33

Please help! I am getting desperate. Dead | X|

Hello, here is my situation:

I have a normal C++ program that has an instance of a COM object (my own), IMyObject

I have another out-of-process COM server, which exposes a COM object IMyOtherObject. IMyOtherObject is held by my C++ program.

So, I end up with this in my C++ program:

void main()
{
IMyObject
IMyOtherObject
}

Now, IMyOtherObject needs to use IMyObject.

How do I pass IMyObject to IMyOtherObject?

Is this possible?

where should I look?

HELP
Jeremy.

"Hey man, Taliban, Tali me Banana."

Re: Passing a COM interface to an out of process COM object

John Smith11-Oct-01 5:06

John Smith

11-Oct-01 5:06

If you are using MFC, you can use LPDISPATCH as the type in your odl file.

Use this to pass your other COM Interface

Re: Passing a COM interface to an out of process COM object

Shadi Al-Kahwaji11-Oct-01 5:30

Shadi Al-Kahwaji

11-Oct-01 5:30

Hi,

If you cannot send the Interface becuase you don't find a data type to send it, then there is no problem. If you want to send IMyObject interface to IMyOtherObject interface, you have to define method to do this in IMyOtherObject like this:

STDMETHOD(SetIMyObjectInterface)(IMyObject *pMyObject);

The problem here that you might compile this using the .h and .c of the IMyObject, but you will face a problem inside the .IDL file, which is IMyObject is undeclared.

To solve this problem, move IMyOtherObject section in the IDL to the type library body:

library MYLIBLib
{
....
//Don't forget to import IMyObject type library here to define the IMyObject Interface

interface IMyOtherObject : IDispatch
{
SetIMyObjectInterface(IMyObject *pMyObject);
}
....
}

I guess this would help you to pass an com interface to another com component.

If this does not answer your question, please, re-phrase your question.

Regards,
ShadiK.

Shadi Al-Kahwaji

Re: Passing a COM interface to an out of process COM object

Marc Britten11-Oct-01 7:08

Marc Britten

11-Oct-01 7:08

pass it as an IUnknown* then queryinterface for IMyObject when you get it.

Re: Passing a COM interface to an out of process COM object

Jeremy Pullicino11-Oct-01 21:13

Jeremy Pullicino

11-Oct-01 21:13

I tied this (I am trying everything!)

Its the best results I got so far.

I pass the IUnkown* , and on the other side I queryinterface.

before passing IMyObject, I do this:

myObj.QueryInterface(IID_IUnknown,&pUnk);

Then I pass pUnk to IMyOtherObject.

This is how I do the queryinterface in IMyOtherObject:

pUnk->QueryInterface(__uuidof(IMyObj),reinterpret_cast _void**> &pMyObj))

However, when I queryinterface I get the error "The interface is unknown."

Am I doing it right?

Jeremy.

"Hey man, Taliban, Tali me Banana."

Re: Passing a COM interface to an out of process COM object

Jeremy Pullicino11-Oct-01 22:44

Jeremy Pullicino

11-Oct-01 22:44

OK. I did some more research: (I bought Inside Distributed COM - Guy Eddon, Henry Eddon, MS Press).
A Very good book.

I came across a section: Marshalling Interface Pointers.

It says that taking an IMyObject interface pointer and return it to a client in another process is not possible. He says: "What constitutes a valid interface pointer in one apartment is complete gibberish in another."

I think will have to re-create the V-table and do some other stuff.

Jeremy.

"Hey man, Taliban, Tali me Banana."

Re: Passing a COM interface to an out of process COM object

13-Oct-01 15:39

You can generate a proxy stub DLL which will allow the interface to be marshalled. It is indeed very possible to pass interface pointers across, and it is very easy. I do it all the time.

For the answers to this, and pretty much any other question about COM, I would HIGHLY recommend Essential COM by Don Box as THE book on COM.

SysFreeString

10-Oct-01 23:10

While doing some testing to make a bit of code bullet proof, I decided to use IsBadReadPtr to check if a BSTR is invalid. While everything for null and uninitialised BSTRs is fine, after calling SysFreeString, IsBadReadPtr still says that the BSTR is fine. Also multiple calls to SYsFreeString with the same BSTR succeed without error. I thought the memory was supposed to be allocated on the SysFreeString call?

Cheers,

Steve

Even if you're not paranoid, they might still be watching you.

Re: SysFreeString

13-Oct-01 15:41

IsBadReadPtr only checks that the pointer points into a valid memory page. After freeing memory the page in which the memory was may still be valid. Hence the "false" positive.

DCOM security on XP

Tim Smith9-Oct-01 13:02

Tim Smith

9-Oct-01 13:02

Does anybody have any examples of DCOM security configurations for XP in a workgroup? (Yes, they are different from 2000. The same settings I use on 2000 do not work on XP.)

I finally got the bloody thing to at least return an interface. But when I do a QueryInterface on that interface, I get E_ACCESSDENIED.

I ... AM ... GOING ... INSANE ...

Tim Smith
Descartes Systems Sciences, Inc.

How to add new icons to the existing ms-word application

RamiReddy8-Oct-01 20:25

RamiReddy

8-Oct-01 20:25

Hi ,
I have a questtion on microsoft-word appliaction.
I need to add my own icon to the existing ms-word application and when i click on that some message box should pop up. I don't know how to manipulate the existing ms-word application. Please help me how to do this.

and one more thing when i install some application like wordweb in my system that icon automatically adding to ms-word.and i write some text into word and select that after that when i click on that icon it is trying to find the meaning of that text. It is just an .Exe application.

so plz guide me how to do this.....
If u have any examples plz send me.

waiting for your early response....

Regards,

Re: How to add new icons to the existing ms-word application

Shadi Al-Kahwaji11-Oct-01 3:18

Shadi Al-Kahwaji

11-Oct-01 3:18

Hi,

I guess what you meant by icon is an Add-In to the MS Word "Added Toolbar with icons". Ok, if this your question, then you can use the VB to create an Add-In toolbar which can be deployed and installed later on to be part of MS Word Add-Ins. You might need to try this with Visual Basic | New Project | Add-In.

Regards,
ShadiK.

Shadi Al-Kahwaji

DCOM and ConnectionPoint

Firoz8-Oct-01 2:31

Firoz

8-Oct-01 2:31

Hi,

I have an ATL component.
My Client is a standard VB application.

The component fires events.
Events are directly handled by VB Client.

This works fine as long as the component
is a local server.

I want to use this component from a remote
machine..

But when I make it a remote server,
I get the error, "PERMISSION DENIED"

I tried all possible combinations in
DcomCnfg Dialog.

I specified the permissions (in Security Tab).

I tried "Interactive & Launching User" Identities
but it gives the same error.

But when I specify the Username & password of
the client machine, it creates an instance of
server on Host machine...
...But it hangs after that..

Can anyone help me out ....

Is it that one cannot use Connection points
in Dcom ... Confused | :confused:

Please some body reply to this message....

Firoz.

Re: DCOM and ConnectionPoint

Rashid Thadha9-Oct-01 2:35

Rashid Thadha

9-Oct-01 2:35

With Connection Points you have too have the right Security Setting on both machines.

Essentially it is a two way duplex communication system

Machine A must have right to Machine B

and

Machine B must have rights to Machine A

Check you security settings on both Machines

Re: DCOM and ConnectionPoint

Tim Smith9-Oct-01 13:03

Tim Smith

9-Oct-01 13:03

You can programatically correct this problem. I will try to remember to post the code I use. If you don't hear from me in a day or two, send me an email.

Tim Smith
Descartes Systems Sciences, Inc.

Last Visit: 31-Dec-99 18:00 Last Update: 29-Jun-24 0:59

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