Re: passing connection points parameters by ref - COM Discussion Boards

1-Dec-01 8:38

Does anyone know the trick to getting a connection point method to pass parameters by reference? Below is an example of a simple event, which should return a short from the client, but the variant varResult always returns empty?!?

Any ideas?

IDL:
[
uuid(48053E7C-D307-40D2-A380-3B9CB25282AB),
version(1.0),
helpstring("atl_event 1.0 Type Library")
]
library ATL_EVENTLib
{
importlib("stdole32.tlb");
importlib("stdole2.tlb");

[
uuid(224E5ED5-D64E-4556-A785-5ACE0DD8F0B3),
helpstring("_IEventTestEvents Interface")
]
dispinterface _IEventTestEvents
{
properties:
methods:
[id(1), helpstring("method TestEvent")] HRESULT TestEvent([in, out] short* sVar );
};

[
uuid(840EF1AE-F80F-4F71-9802-03DFE6555B19),
helpstring("EventTest Class")
]
coclass EventTest
{
[default] interface IEventTest;
[default, source] dispinterface _IEventTestEvents;
};
};

C++:

template <class t="">
class CProxy_IEventTestEvents : public IConnectionPointImpl<t, &diid__ieventtestevents,="" ccomdynamicunkarray="">
{
//Warning this class may be recreated by the wizard.
public:
HRESULT Fire_TestEvent(SHORT * sVar)
{
CComVariant varResult;
T* pT = static_cast<t*>(this);
int nConnectionIndex;
CComVariant* pvars = new CComVariant[1];
int nConnections = m_vec.GetSize();

for (nConnectionIndex = 0; nConnectionIndex < nConnections; nConnectionIndex++)
{
pT->Lock();
CComPtr<iunknown> sp = m_vec.GetAt(nConnectionIndex);
pT->Unlock();
IDispatch* pDispatch = reinterpret_cast<idispatch*>(sp.p);
if (pDispatch != NULL)
{
VariantClear(&varResult);

pvars[0] = *sVar;

DISPPARAMS disp = { pvars, NULL, 1, 0 };
pDispatch->Invoke(0x1, IID_NULL, LOCALE_USER_DEFAULT, DISPATCH_METHOD, &disp, &varResult, NULL, NULL);
}
}
delete[] pvars;
// *sVar = varResult.iVal;
return varResult.scode;

}
};

__scott

Anders Molin1-Dec-01 10:56

1-Dec-01 10:56

SPENNER wrote:
[id(1), helpstring("method TestEvent")] HRESULT TestEvent([in, out] short* sVar );

Woops, you can't have out parameters on a connection point event function...

If you need a parameter back from the client, you need to implement a callback interface instead of using connection points.

- Anders

Money talks, but all mine ever says is "Goodbye!"

SPENNER1-Dec-01 11:38

1-Dec-01 11:38

That's odd...

Because, and I know this isn't the best example, but if I create a quick COM object with VB and define an outgoing interface with a byref parameter, it works great. The resulting IDL is below:
[id(0x00000001)]
void TestEvent(
[in] short eventByVal,
[in, out] short* eventAsRef,
[in, out] VARIANT_BOOL* eventBoolRef);

So, I'm thinking there must be a C++/ATL equivalent, but I can't figure it out...I know I could use a call back interface, but using a connection point would make it more straight forward from the client side...

Any idea how to get this to work?

__scott

Anders Molin1-Dec-01 12:50

1-Dec-01 12:50

SPENNER wrote:
Any idea how to get this to work?

Nope, not right now. I have the "Inside ATL" book, but I left it at work...

I'll try to see if there's a solution in there... (on monday when I get to work...)

- Anders

Money talks, but all mine ever says is "Goodbye!"

Michael P Butler2-Dec-01 1:54

Michael P Butler

2-Dec-01 1:54

Are you sure that VB has generated a connnection point and not a custom event handler?

Michael Smile | :)

SPENNER2-Dec-01 9:51

2-Dec-01 9:51

That's one of the problems with VB, it's hard to know exactly what's going on.
I guess my question should be, how do I create an event function that returns parameters from the client (without using a callback interface)?

Anyone have a clue on this one?

__scott

Anders Molin2-Dec-01 10:55

2-Dec-01 10:55

Why not just use the callback interface. It's easy to make in VC, and easy to use from VB...

- Anders

Money talks, but all mine ever says is "Goodbye!"

SPENNER4-Dec-01 7:56

4-Dec-01 7:56

One of the good things about using connection points is that the client doesn't need to manage the connection to the incoming interface.

That is, to connect to the COM server callback interface, the client must pass a reference of itself to the server. Is there a way for the server to determine if the client is still there before calling the callback function? Is there a way for the server to implicitly connect to the client when the client instantiates an object from the server?

I'm not sure that made sense...oh well

__scott

Anders Molin4-Dec-01 8:11

Using ActiveX Object inside ATL COM Object... Please Help

4-Dec-01 8:11

SPENNER wrote:
I'm not sure that made sense...oh well

I know exactly what you mean. I just don't know of a solution...

- Anders

Money talks, but all mine ever says is "Goodbye!"

Matt Philmon30-Nov-01 18:37

Matt Philmon

30-Nov-01 18:37

We have a communications ATL COM DLL used in a project here that used to load a Java COM object (on a web server) that communicates to a server running IMS transactions on a mainframe. The Java "object" was provided by the customer. Recently they "upgraded" to a newer component, an ActiveX DLL written in Microsoft J++. The old component wasn't a DLL, but a huge collection of Java class files. Because we couldn't import any DLL and had no Type Library to work with we had to do it the painful way, loading by ProgID (easy in VB, hard in ATL), getting the IDispatch pointer, and using Invoke.

This new version comes as a DLL which means I can easily #import the DLL itself and use that to make me a good ol smart pointer which I can use. That part was easy and appears to be fine. My smart pointer is using a single method in the new object called "processITOC". Visual Assist shows me that format of this sucker is:
_bstr_t processITOC ( BSTR * templatepath, BSTR * server, BSTR * port, BSTR * system, BSTR * UserId, BSTR * password, long * timeout, VARIANT * request, BSTR * sTranName );

Seems easy enough... more or less, I hate variants. However, every time I try to pass in the data, it blows with an Access Violation in MSVBVM60.DLL, 0xC0000005. I know this new DLL works fine because I can load it up in a VB project and use it just fine. However, in ATL it blows. I think I'm probably doing something really simple wrong but am currently lost. Could someone give me a hand?

_bstr_t Ret;
BSTR Template = L"file:///C:\\HostTemplates/";
BSTR LogDir = L"C:\\LOG\\";
BSTR Priority = L"3";
BSTR Mainframe = L"111.111.111.111";
WCHAR wchPort[10];
_itow(32000, wchPort, 10);
BSTR Port = wchPort;
BSTR User = L"user";
BSTR Password = L"password";
long Timeout = 240000;
BSTR System = L"DatabaseName";
BSTR TransID = L"ID";

VARIANT upArg;
VariantInit(&upArg);
V_VT(&upArg) = VT_BSTR;
V_BSTR(&upArg) = SysAllocString("ImAnXMLRequestwithtags");

m_pIHandler->setLoggingDirectory(&LogDir);
m_pIHandler->setLoggingPriority(&Priority);

Ret = m_pIHandler->processITOC( &Template,
&Mainframe,
&Port,
&System,
&User,
&Password,
&Timeout,
&upArg,
&TransID );

If someone could point something out I'd be grateful.

Thanks,
Matt

WinXP

Gfw30-Nov-01 2:39

Gfw

30-Nov-01 2:39

I have a COM object that returns a string to the calling program. It works perfectly under Win95(a) to Win2000. Under WinXP pro, it crashes in oleauto32 if returned as a BSTR, but passes successfully if passed as a safearray.

Any ideas? Thanks.

How to version an ActiveX dll?

David Stranz29-Nov-01 13:19

David Stranz

29-Nov-01 13:19

We have an ActiveX DLL containing both full controls and simple objects, implemented in C++ / ATL.

We've updated the library, and want to assign a new version number (say 2, instead of 1). If we edit the RGS and IDL files to reflect the new version number, our users find that the full controls aren't instantiated unless the registry contains the -old- version keys. When a VB project using the controls is opened, it recognizes that an updated version has been registered (asks if you want to update the project), but then can't instantiate the full controls.

There is no problem with simple controls, since there is no version number info for them in their registry entries. The problem is only exhibited with full controls.

What are we doing wrong? We've searched everywhere we can think of in MSDN and elsewhere for how to do this, but can't find any info. If someone can either answer or point us to documentation, we'd be greatly appreciative.

David Stranz

ActiveX & Threads...gettin' Funky - Check this Out.

Tim Rymer28-Nov-01 11:29

Tim Rymer

28-Nov-01 11:29

I've got this ActiveX Object (made w/ VC++6.0), it creates a thread (so i can have multiple running at the same time), but it also fires events to my Visual Basic App. With me creating threads cause problems for those events trying to get back to the application?

It seems that way. VB seems to crash when i Fire an event. When i use an activex control, does it have its own thread? Can i redirect the thread ID or something like that? It's just being flat out weird. Has anyone had the same trouble before? I set up connection points at the beginning when i made the obj., is there any other settings that i need to have? Even a little bit of help will go a long way for me...Thanks Y'all. Big Grin | :-D

~TIM!

SHABBA!!

Re: ActiveX & Threads...gettin' Funky - Check this Out.

Anders Molin30-Nov-01 23:40