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I have little experience with COM and am trying to build my knowledge in this department
The plan :
Create a COM object which will handle writing records and deleting records from a file.
What I've done so far:
(I didn't get very far) I created a new ATL COM AppWizzard project. Then I inserted a new simple Simple ATL Object. This created my interface. I then tried to add the following function to the interface:
HRESULT writeRecord (char * record, int recordLength)
The Problem:
After doing this I compiled the project and got the following error:
template <class t1="">
class CComCreator
{
public:
static HRESULT WINAPI CreateInstance(void* pv, REFIID riid, LPVOID* ppv)
{
ATLASSERT(*ppv == NULL);
HRESULT hRes = E_OUTOFMEMORY;
T1* p = NULL;
ATLTRY(p = new T1(pv))//--------------> Error occurs here!!
if (p != NULL)
{
p->SetVoid(pv);
p->InternalFinalConstructAddRef();
hRes = p->FinalConstruct();
p->InternalFinalConstructRelease();
if (hRes == S_OK)
hRes = p->QueryInterface(riid, ppv);
if (hRes != S_OK)
delete p;
}
return hRes;
}
};
"c:\program files\microsoft visual studio\vc98\atl\include\atlcom.h(1827) : error C2259: 'CComObject<class cfileeditor="">' : cannot instantiate abstract class due to following members:
c:\program files\microsoft visual studio\vc98\atl\include\atlcom.h(1823) : while compiling class-template member function 'long __stdcall ATL::CComCreator<class atl::ccomobject<class="" cfileeditor=""> >::CreateInstance(void *,const struct _GUID &
,void ** )'"
My Guess:
The compiler doesn't like the char* parameter in the function. I added some functions successfully, however none of them received a char* as an argument
Could someone explain this to me?
Thank you
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not sure about the compiler error, but you're right that COM doesn't like "char *". COM likes "BSTR"s for strings. this is a length-prefixed string with two bytes per character. it's not a C=style string by any means.
you should take a look at classes like _bstr_t or CComBSTR.
actually, that compiler error probably says that the IDL file or your ATL object's .h file is declaring something that you haven't implemented.
-c
------------------------------
Smaller Animals Software, Inc.
http://www.smalleranimals.com
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Alright I've changed things around so that my function looks as follows:
HRESULT writeRecord(BSTR record, int recordLength, BSTR fileName)
Function definition is:
// FileEditor.cpp : Implementation of CFileEditor
#include stdio.h
#include comdef.h
#include "stdafx.h"
#include "FileEdit.h"
#include "FileEditor.h"
/////////////////////////////////////////////////////////////////////////////
// CFileEditor
STDMETHODIMP CFileEditor::writeRecord(BSTR record, int recordLength, BSTR fileName)
{
FILE * file = NULL;
_bstr_t fName = fileName;
char * pFName = fName.operator char *fName;
file = fopen(fileName, "r+");
return S_OK;
}
Now for some reason the compiler doesn't recognize the _bstr_t data type (even though I have included the comdef.h file).
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try swapping the stdafx.h and comdef.h includes.
-c
------------------------------
Smaller Animals Software, Inc.
http://www.smalleranimals.com
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What is the exact error message?
Does the following code make any difference
_bstr_t fName(fileName);
char* pFName = (char*) fName;
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EUREKA!!!
THANKS GUYS!
The cause of the problem was that stdafx.h wasn't the first file include.
the result:
// FileEditor.cpp : Implementation of CFileEditor
#include "stdafx.h"
#include stdio.h
#include comdef.h
#include "FileEdit.h"
#include "FileEditor.h"
/////////////////////////////////////////////////////////////////////////////
// CFileEditor
STDMETHODIMP CFileEditor::writeRecord(BSTR record, int recordLength, BSTR fileName)
{
FILE * file = NULL;
_bstr_t fName = fileName;
char * pFName = fName.operator char *();
file = fopen(pFName, "r+");
return S_OK;
}
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Hi!
We have :
typedef struct Str_ {
int array[100];
int n;
//...
} Str;
and a member variable Str x;
I want x to be exported into
an ActiveX control, using Visual C++6, and I don't know what
is the appropriate last parameter in the DISP_PROPERTY macro.
Wish for help!
Thanks!
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Hi,
I might look a bit selfish here, but,
have you tried this ?
www.codeproject.com\atl\udtdemo.asp
Hope this helps
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Okay, this is a bit of a stab in the dark kind of question so my apologies if it isn't clearly worded.
I have an MFC application that calls a COM object (ATL). The MFC app calls a method
m_pOutlook->IDCaller(sPhoneNumber, &sCallerName).
The COM object looks up in the Outlook database for the phone number and returns the name.
Now I need to have a choice between using Outlook and using Goldmine. This has brought up the idea that the software can talk to multiple contact managers, not just the two mentioned.
So I'd like to write the system so that I can just plug new COM objects in like Word and Visual Studios Addins whenever somebody wants another contact manager.
Anybody know where I can find some good info on developing applications to support COM addins. Any books or articles out there to do this kind of thing? It is possible that a third party might want to write addins too.
My idea is to have a list of CLSID, and query them for the required interface. I'm just not sure about the best way to do this.
Michael 
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Have you checked out this old msj article at http://www.microsoft.com/msj/0797/snapins.htm?
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I've been pulling my hair out this past two weeks in an attempt to find some kind of answer under this rug that rest so comfortably on my head.
The problem I'm having is setting my COM+ component as a server under the Component Service Manager. The component has a method that returns an ADO::_Connection pointer. My two test clients, written in VB an VC, take the returned _Connection pointer and perform a simple SQL store procedure call LOOP, which waits for 1 minute.
The VB client does just fine, probably taking care of all the marshalling in the background. Unfortunately, the VC client doesn't do the same. It throws a "NULL reference pointer pass to stub" exception when I try to execute the store procedure.
Below is the code to the component method call by the clients
STDMETHODIMP CSpeedLink::GetDBConnection(_Connection **ppSLDBConnection)
{
GetID(&m_bstrSpeedLinkID);
GetConnectionString(&m_slConnection);
// ASSERT: Retrieve SpeedLink id and connection string from the registry
if ((m_pConnectionPtr != NULL) && (m_pConnectionPtr->State == adStateOpen))
m_pConnectionPtr->Close();
// ASSERT: Closes any previously open connection
bool bConnected = FALSE;
while (!bConnected)
{
try
{
if (m_pConnectionPtr == NULL)
m_pConnectionPtr.CreateInstance(__uuidof(Connection));
// ASSERT: Instantiate connection if NULL
m_pConnectionPtr->Open(m_slConnection.ConnectionString,
TEXT(""), TEXT(""), adOpenUnspecified);
*ppSLDBConnection = m_pConnectionPtr.GetInterfacePtr();
bConnected = TRUE;
// ASSERT: Returns an opened db connection if successful.
}
catch (_com_error &error)
{
if (error.Error() == E_TIMEOUT)
{
error = NULL;
Sleep(5000);
// ASSERT: DB server busy try again in 5 seconds
}
else
{
error = NULL;
return E_FAIL;
// ASSERT: Error opening db connection
}
}
}
return S_OK;
}
The VB client code that calls the method above is as follow
Dim speedLink As New OALib.speedLink
Dim objConn As New ADODB.Connection
' ASSERT: Initialization
btnTestConnection.Enabled = False
Set objConn = speedLink.GetDBConnection
btnTestConnection.Enabled = True
' ASSERT: Connect to the SpeedLink database
If objConn.State = adStateOpen Then
objConn.CommandTimeout = 0;
objConn.Execute "exec loop", ,adCmdText
objConn.Close
MsgBox ("Successfully connected to SpeedLink database.")
' ASSERT: The connection was made successfully
Else
MsgBox ("Unable to connect to SpeedLink database.")
' ASSERT: Error - Unable to connect to the server
End If
Set objConn = Nothing
Set speedLink = Nothing
Similarly, the VC client code that calls the method is as follow
try
{
CoInitialize(NULL);
HRESULT hResult;
ISpeedLink FAR* pISpeedLink = (ISpeedLink FAR*)NULL;
_ConnectionPtr pConnection;
hResult = CoCreateInstance(CLSID_SpeedLink, NULL, CLSCTX_SERVER,
IID_ISpeedLink, (void FAR* FAR*)&pISpeedLink);
pConnection = pISpeedLink->GetDBConnection();
if (pConnection != NULL)
{
pConnection->CommandTimeout = 0;
pConnection->Execute("exec loop", NULL, adCmdText);
// ASSERT: Crashes at this line, when trying to execute procedure
pConnection->Close();
}
CoUninitialize();
}
catch (_com_error &error)
{
MessageBox(error.ErrorMessage(), "Error1", MB_OK);
}
MessageBox("Complete", "All Thread", MB_OK);
Note: A trace is placed on the SQL 2000 Server to verify the execution of the store procedure.
Note: The code
*ppSLDBConnection = m_pConnectionPtr.GetInterfacePtr();
was also replaced with
*ppSLDBConnection = m_pConnectionPtr.Detach();
both works flawlessly in VB but not in VC.
Now, down on my knee, I plea to any kind soul for a guiding hand and offer much needed help. Maybe, just maybe, I won't go bald after all.
Much thanks in advance for any help you can offer. Thank you.
  
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You must to Create the Instance of the connection in your client.
CreateInstance(__uuidof(Connection));
This work in VB because when you do New ADODB.Connection VB instance the Connection in the client. A new Connection.
In VC Aplication you get the aconnection from the Server, but the conncetion is in the server, and not in the Client app....
I hope to help you.
Carlos Antollini.
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Carlos, thank you for your prompt reply.
I have tried CreateInstance(__uuidof(Connection));
before, but that didn't solve the problem.
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The code below, takes a parameterized object name, looks for a specific interface
and trys to call its methods.
It finds the interface with no difficulty but gets the error 0x8007806ba
(The RPC server is unavailable. ).
The same calls work from a VB test script. I'm running this on a Windows 2k server
with SP 2. I've checked all the security parameters (DCOMCNFG) all are set to
default, the same as for the other objects that work fine...
This code used to work, I've modified the object, transfered it to a new program
and now it fails. I did change the name of the interface (I seperated the methods
out from another interface). So I tried the old object, everything works fine. (difference shown as commente line (//OLD.)
It would appear there is something wrong with my new object. I would think the
problem must be in the new object, except that I wrote a VB test app, and it works fine. This makes me think the problem is NOT in the object.
Please Help!!
I'd include the code for the object, but its large, and I'm not sure which parts would be useful...
Thanks, Bill
*******************************************************************************************
This VB code works fine
Dim apminfo As New APMOBJECTLib.MessageInfo
Private Sub Command1_Click()
Dim t As String
t = apminfo.GetFunction("sfddsfsdlfksdflk")
End Sub
*****************************************************************************************
This code locates and connects to the interface (MessageInfo). Every thing here succeeds...
CErrorInfo CServiceMessage::UnpackMessage(VARIANT vBody)
{
CErrorInfo err;
CoInitialize(NULL);
VARIANT vResult;
_bstr_t bstrValue;
m_strBody = GetMessageAsString(vBody);
try
{
// Get Function handler object
CLSID ID;
m_pBroker=NULL;
//OLD CString strObjName = "APMObj.CFunction"; // This works fine when activated
CString strObjName = "APMObject.MessageInfo"; // New object.
// The following line of code succeeds
HRESULT hr = CLSIDFromProgID( strObjName.AllocSysString(), &ID);
if (hr != S_OK)
{
LPTSTR lpMsgBuf;
CString strError;
if (FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
NULL, hr,
MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
(LPTSTR) &lpMsgBuf, 0, NULL ) == 0 ) // Couldn't find error code
{
lpMsgBuf = "Unknown Error";
}
strError.Format("%s: %s %s Error %d: %s.","CConfigServices::Load()",
"Attempting to find object ", m_pParent->m_strObjectName,
hr, lpMsgBuf);
err.SetError(ERR_SEVERITY_MAJOR, CONFIGERROR + CString(strError));
LocalFree(lpMsgBuf);
return err;
}
hr = CoCreateInstance(ID, NULL, CLSCTX_LOCAL_SERVER,
IID_IDispatch, (void **)&(m_pBroker));
if (hr != S_OK)
{
// error handling
}
vResult = GetValue(vBody,CString("GetPriority"),VT_I4);
*******************************************************************************
This code fails
VARIANT CServiceMessage::GetValue(VARIANT vBody, CString strField, int iType)
{
DISPID dispID;
HRESULT hr;
CErrorInfo err;
LPOLESTR olestr;
VARIANT vResult;
try
{
// Unpack function name
olestr = strField.AllocSysString();
TRACEX("Get ID of " + strField);
// the following line of code fails if the new object and interface is used. It works if
// the old object name and interface is used.
hr = m_pBroker->GetIDsOfNames(IID_NULL, &olestr, 1, LOCALE_USER_DEFAULT,
&dispID);
if (hr != S_OK)
// hr is = 0x800706ba (RPC Server Not Found)![Rose | [Rose]](https://codeproject.global.ssl.fastly.net/script/Forums/Images/rose.gif)
Thanks for the help,
Bill
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The code below, takes a parameterized object name, looks for a specific interface and trys to call its methods.
It finds the interface with no difficulty but gets the error 0x8007806ba
(The RPC server is unavailable. ).
The same calls work from a VB test script. I'm running this on a Windows 2k server with SP 2. I've checked all the security parameters (DCOMCNFG) all are set to default, the same as for the other objects that work fine...
This code used to work, I've modified the object, transfered it to a new program and now it fails. I did change the name of the interface (I seperated the methods out from another interface). So I tried the old object, everything works fine. (difference shown as commente line (//OLD.)
It would appear there is something wrong with my new object. I would think the problem must be in the new object, except that I wrote a VB test app, and it works fine. This makes me think the problem is NOT in the object.
Please Help!!
I'd include the code for the object, but its large, and I'm not sure which parts would be useful...
Thanks, Bill
*******************************************************************************************
This VB code works fine
Dim apminfo As New APMOBJECTLib.MessageInfo
Private Sub Command1_Click()
Dim t As String
t = apminfo.GetFunction("sfddsfsdlfksdflk")
End Sub
*****************************************************************************************
This code locates and connects to the interface (MessageInfo). Every thing here succeeds...
CErrorInfo CServiceMessage::UnpackMessage(VARIANT vBody)
{
CErrorInfo err;
CoInitialize(NULL);
VARIANT vResult;
_bstr_t bstrValue;
m_strBody = GetMessageAsString(vBody);
try
{
// Get Function handler object
CLSID ID;
m_pBroker=NULL;
//OLD CString strObjName = "APMObj.CFunction"; // This works fine when activated
CString strObjName = "APMObject.MessageInfo"; // New object.
// The following line of code succeeds
HRESULT hr = CLSIDFromProgID( strObjName.AllocSysString(), &ID);
if (hr != S_OK)
{
LPTSTR lpMsgBuf;
CString strError;
if (FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
NULL, hr,
MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
(LPTSTR) &lpMsgBuf, 0, NULL ) == 0 ) // Couldn't find error code
{
lpMsgBuf = "Unknown Error";
}
strError.Format("%s: %s %s Error %d: %s.","CConfigServices::Load()",
"Attempting to find object ", m_pParent->m_strObjectName,
hr, lpMsgBuf);
err.SetError(ERR_SEVERITY_MAJOR, CONFIGERROR + CString(strError));
LocalFree(lpMsgBuf);
return err;
}
hr = CoCreateInstance(ID, NULL, CLSCTX_LOCAL_SERVER,
IID_IDispatch, (void **)&(m_pBroker));
if (hr != S_OK)
{
// error handling
}
vResult = GetValue(vBody,CString("GetPriority"),VT_I4);
*******************************************************************************
This code fails
VARIANT CServiceMessage::GetValue(VARIANT vBody, CString strField, int iType)
{
DISPID dispID;
HRESULT hr;
CErrorInfo err;
LPOLESTR olestr;
VARIANT vResult;
try
{
// Unpack function name
olestr = strField.AllocSysString();
TRACEX("Get ID of " + strField);
// the following line of code fails if the new object and interface is used. It works if
// the old object name and interface is used.
hr = m_pBroker->GetIDsOfNames(IID_NULL, &olestr, 1, LOCALE_USER_DEFAULT,
&dispID);
if (hr != S_OK)
// hr is = 0x800706ba (RPC Server Not Found)
Thanks for the help,
Bill
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Sorry for the double post. My browser reported an error the first time...
I thought it didn't post.
Thanks for the help,
Bill
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I have a COM server and client, both running on the same box. When I try to run the client on a Windows 2000 server, I get the RPC Server Unavailable message. This happens when I try to get the dispid of the method name (GetIDsFromNames). All the calls up til then work fine (CoCreate etc.)
I threw together a VB app to test it. Works fine.
I moved both to NT4. Works fine.
Obviously there is something my C++ client needs to do for W2k that is different. Any body know what that might be???
Help, this is driving me nuts...
Thanks for the help,
Bill
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Sorry, I pushed the wrong button, here is the entire post. Pleasd ignor this. I'll repost.
Thanks for the help,
Bill
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Does anybody know a reliable tool that traces COM?
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Hi,
I have a dialog based app (maindlg is CPropertySheet) and I want to add accelerators to the pages. How is this done in WTL?
Thanks,
Remon
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Yes, I'am aware of this function, but is doesn't work in a modal property sheet.
Remon
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Hi!
I am trying to create an out of process server which runs as a remote service. So, I have created the service on machine B.
The client is on machine A, and has been compiled using #include (with the _i.c and .h) files. The service (on machine B) has been initialized as follows:
a. nmake the *ps.mk file
b. regsvr32 the *ps.dll file
c. Run *.exe -service
d. and finally start the service on machine B.
On machine A(client), I do the following:
CoInitialize(NULL);
LPWSTR pwszName="name of machine B;
COSERVERINFO csi={0,pwszName,NULL,0};
MULTI_QI mqi[]={{&IID_ITestInterface,NULL,S_OK}};
try{
HRESULT hr=CoCreateInstanceEx(CLSID_TestInterface,NULL,CLSCTX_SERVER,
&csi,sizeof(mqi)/sizeof(mqi[0]),mqi);
if(FAILED(hr)) _com_issue_error();
//use a smart pointer and do some method invokation..
}
catch(_com_error&error){
// display error
}
when I run this, I get the error that Interface not registered 80040155.
Can someone point out what is going wrong here. My main query is whether this error is generated from the client side (machine A), indicating that the interface should be registered on machine A, or it is generated from the server itself.
Ideas/comments would be greatly appreciated.
thanks in advance
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hello,
i think that the *PS.dll is not registered in the client machine. So copy the ps dll in the client machine and register it and try running it. If error persists please report so that i can think of something else.
Ganesh.M.Ramaswamy
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