COM Discussion Boards

25-Mar-05 13:58

I am currently writing a program in C++ which uses the iTunes COM interfaces from the iTunes COM SDK (http://developer.apple.com/sdk/itunescomsdk.html). I have found it easy to use IiTunes (CoInitialize(NULL); CoCreateInstance(CLSID_iTunesApp, NULL, CLSCTX_LOCAL_SERVER, IID_IiTunes, (PVOID *)&iITunes);), but using _IiTunesEvents poses some adversity. I would like the OnAboutToPromptUserToQuitEvent to call a function where I can run some cleanup code. How can I implement _IiTunesEvents? I am used to C# where I can use += easily, but it is my understanding that COM requires sinks and things of that sort.

I want to have something like this:
IiTunes *iITunes = NULL;
//make object bla bla bla
??????????(OnAboutToPromptUserToQuitEvent);

.....

HRESULT OnAboutToPromptUserToQuitEvent()
{
.....
}

Thanks,
Jason A. Donenfeld
ZX2C4 Software

http://msdn.microsoft.com/library/en-us/com/htm/events_27cd.asp?frame=true[^]

Gerald Schwab25-Mar-05 14:30

Gerald Schwab

25-Mar-05 14:30

zx2c425-Mar-05 15:05

25-Mar-05 15:05

thanks so much. ill read through that.

any sample code?

zx2c426-Mar-05 6:35

26-Mar-05 6:35

This is what I have currently:

HRESULT hres;
DWORD d;
IConnectionPoint * icp;
IConnectionPointContainer * icpc;
hres = iITunes->QueryInterface(IID_IConnectionPointContainer,(PVOID *)&icpc);
hres = icpc->FindConnectionPoint(DIID__IiTunesEvents,&icp);
eventSink = new ITunesEventSink();
hres = icp->Advise((IUnknown*)&eventSink,&d);

and then
class ITunesEventSink:public _IiTunesEvents
{
public:
HRESULT OnAboutToPromptUserToQuitEvent();
};

The only problem is that "error C2259: 'ITunesEventSink' : cannot instantiate abstract class" Well duh, I need to impliment all of the virtual functions, but does that mean looking at the header files containing IDispatch and IUnknown and then copying in all of those function names and then giving functionality to them? If so, what is the best way to go about implimenting the functions?

zx2c426-Mar-05 16:27

Is MDAC new Version backwork compatible?

26-Mar-05 16:27

alright. i implimented the ITunesEventSink and now i have OnAboutToPromptUserToQuitEvent being called; however, it calls it on the wrong thread. Is there way that i can call a function from a different thread?

netboy202025-Mar-05 8:04

netboy2020

25-Mar-05 8:04

Hello,

I have created one ActiveX Dll using VB and I am using Data Access Components 2.5.

After deploying this COM components I could access it through ASP Pages.

Everything goes well in development environment but in Production Environment we are installing MDAC 2.7.
And components are not working.

So I would like to confirm whether MDAC 2.7 installtion program includes MDAC 2.5. And my ActiveX dll having reference to the "Activex Data Access component 2.5" is suppose to work or not.

Thanks
Mitesh

Re: Is MDAC new Version backwork compatible?

John M. Drescher25-Mar-05 8:35

John M. Drescher

25-Mar-05 8:35

MDAC 2.7 is definitly not new, I have been using it for at least a year, probably 2 or 3. I have not noticed any kind of problem with backward compatibility.

[EDIT]
MDAC 2.8 is the latest version. It was first introduced in 8/4/2003 so I guess I have an old version...
[/EDIT]

John

Custom ActiveX control?

foxyspy24-Mar-05 20:23

foxyspy

24-Mar-05 20:23

How to fix (custom ActiveX)control size in design time.

I am using MFC ActiveX ControlWizard.

Please help me.

Thanks

David Park

preparing DISPPARAMS for a method??

Muhammad Azam24-Mar-05 19:00

Muhammad Azam

24-Mar-05 19:00

hi
I am writing an IDispatch client. i want to call this method

void SomeMethod(
[in, out] BSTR* strFile,
[in, out] BSTR* strMiscFile,
[in, out, optional, defaultvalue("Some Default value")] BSTR* strValue
);

using IDispatch::Invoke. I have got DISPID of this method using GetIDsOfNames, the problem is in making DISPPARAMS for this method that can be passed to Invoke.

does any one know how do we prepare DISPPARAMS for such type of methods as mentioned above.

Thanks in anticipation

Azam

Vi227-Mar-05 22:30

Vi2

27-Mar-05 22:30

CComBSTR strFile, strMiscFile, strValue;

VARIANTARG* rgvarg = new VARIANTARG[3];

V_VT(&rgvarg[2]) = VT_BSTR | VT_BYREF;
V_BSTRREF(&rgvarg[2]) = &strFile;

V_VT(&rgvarg[1]) = VT_BSTR | VT_BYREF;
V_BSTRREF(&rgvarg[1]) = &strMiscFile;

V_VT(&rgvarg[0]) = VT_BSTR | VT_BYREF;
V_BSTRREF(&rgvarg[0]) = &strValue;

DISPPARAMS dispparams = { rgvarg, NULL, 3, 0 };

With best wishes,
Vita

Muhammad Azam27-Mar-05 22:47

Muhammad Azam

27-Mar-05 22:47

hi Vita

Thank you very much for solving my problem. One thing i would also like to ask if you donot mind, how do we pass named parametrs to a function. lets say if the function is same as mentioned in my previous question i.e

void SomeMethod(
[in, out] BSTR* strFile,
[in, out] BSTR* strMiscFile,
[in, out, optional, defaultvalue("Some Default value")] BSTR* strValue
);

then how do v prepare DISPPARAMS for this function using named arguments?

thanks in anticipation

Azam

Vi227-Mar-05 23:01

Vi2

27-Mar-05 23:01

Look at Automation: Passing Parameters[^]
But I don't recommend you to use the named arguments.

With best wishes,
Vita

Open excel woorbook in office xp 2002 with c#

Muhammad Azam27-Mar-05 23:06

Muhammad Azam

27-Mar-05 23:06

Thanks once again. i will read this article. may i distrub u if i need some help in between Smile | :)

regards

Azam

24-Mar-05 6:16

Hello, I`ve got a problem with opening excel woorbook using this code.
I`ve got office xp 2002 with sp3.
On one computer i dont have this problem, but on the other one appears exception.

object mis = System.Reflection.Missing.Value;
Excel.Application excel = new Excel.ApplicationClass();
Excel._Workbook wkb = excel.Workbooks.Add(mis);
Excel._Worksheet sht = (Excel._Worksheet)wkb.Sheets[1];

I did add reference to excel 10. TypeLib version 1.4

This is the exception i`ve receive.
An unhandled exception of type 'System.Runtime.InteropServices.COMException' occurred in SqlToExcel.exe

Additional information: Old libary or incorect form.
(Biblioteka w starym formacie lub nieprawidłowy typ biblioteki).

I dont now what to change in the code.

Please, help meeee. Frown | :(

Using COM dll in C

Monty²23-Mar-05 23:54

Monty²

23-Mar-05 23:54

i remember reading an article but i can't remeber where now, how can i use a COM dll in C (not create a COM object in C, just be able to call some functions)
thanks

C makes it easy to shoot yourself in the foot; C++ makes it harder, but when you do, it blows away your whole leg

Jörgen Sigvardsson24-Mar-05 2:52

Jörgen Sigvardsson

24-Mar-05 2:52

A COM DLL is a regular DLL with some restrictions on it: It must export the 5 functions DllMain, DllCanUnloadNow, DllGetClassObject, DllRegisterServer and DllUnregisterServer. Technically, the last function isn't really needed to run COM stuff, but if you want to uninstall the COM DLL, it's nice to be able to remove references to it in the registry.

To load a DLL:

HMODULE hDLL = LoadLibrary(_T("the.dll"));
if(!hDLL) exit(-1); // Error!

To acquire a function pointer to a function inside the DLL:

void (*function)();
function = (void (*)())GetProcAddress(hDLL, "TheNameOfFunction");
if(!function) exit(-1); // Error!
function(); // Call it

And finally, if you are done with the DLL, and you wish to unload it, call

FreeLibrary(hDLL);

There's also LoadLibraryEx which might be interesting to have a look at.

Did I answer your question? The MSDN Library has all the information you need to manuall load and use DLLs.

--
My name in Katakana is ヨルゲン.
My name in German is Jörgen.
My name in Mandarin/Kanji is 乔尔根西格瓦德森.
My name in Korean is 요르겐.

I blog too now[^]

Monty²24-Mar-05 5:20

Monty²

24-Mar-05 5:20

yes by using the above stuff i can create an object

how will i call the interface methods and all the vtbl stuff

thanks for such a neat reply very well explained thanks Big Grin | :-D

C makes it easy to shoot yourself in the foot; C++ makes it harder, but when you do, it blows away your whole leg

Jörgen Sigvardsson24-Mar-05 9:54

Jörgen Sigvardsson

24-Mar-05 9:54

Ah, you meant COM object methods, and not functions exported by the DLL. I see. In that case: what Mike said. Smile | :)

--
My name in Katakana is ヨルゲン.
My name in German is Jörgen.
My name in Mandarin/Kanji is 乔尔根西格瓦德森.
My name in Korean is 요르겐.

I blog too now[^]

Mike Dimmick24-Mar-05 5:43

Mike Dimmick

24-Mar-05 5:43

You use CoCreateInstance as before. To call an instance method, you need the header file generated from the source IDL by midl. Instead of writing, for example

p->GoForward()

you would write

IWebBrowser_GoForward(p)

That is, you prefix the call with the name of the interface and pass the object as the first parameter of the call. IWebBrowser_GoForward is actually a macro that masks the explicit dereference:

p->lpVtbl->GoForward(p)

I'd seriously query why you're using it from C, though - it's perfectly possible to make a hybrid C/C++ app where some modules are compiled as C and others as C++.

[EDIT:] On re-reading the ExDisp.h header file (just an example, it contains the IWebBrowser interface I referred to earlier) it looks like you only get the interface_method macros if you define COBJMACROS. [/EDIT]

Stability. What an interesting concept. -- Chris Maunder