OLE Automation controller example w/BSTRs

Joe Vannucci -- vannuccj@ix.netcom.com
Friday, February 14, 1997

Environment:  VC 1.52c -> VC 4.2b  Win 95

I'm looking for a good sample of an OLE automation controller that calls
server methods with BSTRs as params and return values.  The examples
I've found in the usual places are too simplistic (no BSTRs).  I'm not
clear on the "clean up" of BSTRs from the controller side -- especially
since they can come back as CStrings.  Also not clear on how to pass a
CString as a param to an object method receiving a BSTR.  Also what are
the conversion macros I should use to convert between BSTR and const
char*?

I'm subclassing COleDispatchDriver.

Thanks in advance!
-joe vannucci
vannuccj@ix.netcom.com

---

Deirdre Collins -- deirdre@technicon.com
Sunday, February 16, 1997

Here's a brief sample :

Client side :

	long ccqId;
	CString fileName = file_dlg.GetPathName ();
	BSTR bstrFileName = fileName.AllocSysString ();

	hr = m_pIStorageCCQData->Open (NULL, (LPCTSTR)fileName, &m_pIStorage);
	if (hr == S_OK)
	{
		hr = m_pIStorageCCQData->GetOutputReference (m_pIStorage, &ccqId,
&bstrFileName);
		fileName = bstrFileName;
	}

	SysFreeString (bstrFileName);

Server side:

STDMETHODIMP IOObj::XStorageCCQData::
GetOutputReference (IStorage* pIStorage, long* pCCQId, BSTR*
pCCQFileName)
{
	METHOD_PROLOGUE(IOObj, StorageCCQData)

	HRESULT hr = S_OK;

	CListEntry * entry = m_saveList.Find (pIStorage);

	if (entry)
	{
		if (entry->m_recordId != NO_KEY)
		{
			if (pCCQId)
			{
				*pCCQId = entry->m_recordId;
			}
			else
			{
				hr = ITF_E_INVALIDPARAMETER;
			}
		}
		else if (!entry->m_document.IsEmpty ())
		{
			if (pCCQFileName)
			{
				BSTR bstr = entry->m_document.AllocSysString ();
				SysFreeString (*pCCQFileName);
				*pCCQFileName = bstr;
			}
			else
			{
				hr = ITF_E_INVALIDPARAMETER;
			}
		}
	}
	else
	{
		hr = ITF_E_STORAGEUNKNOWN;
	}

	return (hr);
}


>-----Original Message-----
>From:	Joe Vannucci [SMTP:vannuccj@ix.netcom.com]
>Sent:	Saturday, February 15, 1997 3:04 AM
>To:	mfc-l@netcom.com
>Subject:	OLE Automation controller example w/BSTRs
>
>Environment:  VC 1.52c -> VC 4.2b  Win 95
>
>I'm looking for a good sample of an OLE automation controller that calls
>server methods with BSTRs as params and return values.  The examples
>I've found in the usual places are too simplistic (no BSTRs).  I'm not
>clear on the "clean up" of BSTRs from the controller side -- especially
>since they can come back as CStrings.  Also not clear on how to pass a
>CString as a param to an object method receiving a BSTR.  Also what are
>the conversion macros I should use to convert between BSTR and const
>char*?
>
>I'm subclassing COleDispatchDriver.
>
>Thanks in advance!
>-joe vannucci
>vannuccj@ix.netcom.com

---

David Lowndes -- David.Lowndes@bj.co.uk
Monday, February 17, 1997

>I'm looking for a good sample of an OLE automation controller that calls
server methods with BSTRs as params and return values.  The examples
I've found in the usual places are too simplistic (no BSTRs).  I'm not
clear on the "clean up" of BSTRs from the controller side -- especially
since they can come back as CStrings.  Also not clear on how to pass a
CString as a param to an object method receiving a BSTR.  Also what are
the conversion macros I should use to convert between BSTR and const
char*?
<

Joe,

There's a series of articles on the ms web site, one of which is
"Article 3. Strings the OLE Way" that details using BSTRs in detail.
Have a look at www.microsoft.com/oledev/olecom/article3.htm.

Dave

---

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