CString strText; IMyInterface myOleApp; myOleApp.CreateDispatch("CmyOleApp.App"); myOleApp.myMethod((BSTR*)&strText); ------------------------------------------------------------------------- -------- from my ole app (mine consist of a dialog box that I can input some text): ------------------------------------------------------------------------- -------- CMyDialog* m_pMyDialog; // I save the pointer to the dialog in the constructor CMyDialog* GetMyDialog {return m_pMyDialog;} CString* m_pMyString; void SetMyString(CString* pString) {m_pMyString = pString;} in the interface BOOL CMyInterface::myMethod(BSTR FAR* pString) { ((CmyOleApp*)AfxGetApp())->GetMyDialog()->SetMyString((CString*)pString) ; } So whenever I set the text using m_pMyString, is always pointing to the strText variable in my main app............ I did it this way and it works for me, I'm not sure if this is what you're looking for. Let me know if it worked...... >---------- >From: Giles R. Chamberlin[SMTP:GRC@langley.softwright.co.uk] >Sent: Wednesday, October 23, 1996 10:29 AM >To: mfc-l >Subject: Ole Automation - passing parameters by reference > > >Environment: VC++ 4.1, Win 95 > >I've successfully created a variety of automation methods which allow >me to pass parameters in to an automation function. OK so all I did >was click Class Wizard buttons, but it made me feel happy. > >Now the tricky bit. I'm trying to implement a function which in a pure >C++ world would like: >BOOL Next(CString& strText); > >ie on return strText has something useful in it. Having CString as the >return type is not one of the options I'm after. > >So, moving in to OLE, I used ClassWizard to generate my method and hand >edited the odl file to add [out] to the parameter definition: > > [ uuid(AD3901A0-2747-11D0-AB3C-0020AF71E433) ] >dispinterface ISPageNames >{ > properties: > // NOTE - ClassWizard will maintain property information here. > // Use extreme caution when editing this section. > //{{AFX_ODL_PROP(SPageNames) > //}}AFX_ODL_PROP > methods: > // NOTE - ClassWizard will maintain method information here. > // Use extreme caution when editing this section. > //{{AFX_ODL_METHOD(SPageNames) > [id(1)] void Reset(); > [id(2)] boolean Next([out] BSTR* pbstrPageName); // hand editing here > //}}AFX_ODL_METHOD >}; > > >and coded the function itself as: > >BOOL SPageNames::Auto_Next(BSTR* pbstrPageName) >{ > if(m_posCurrent == NULL) > return FALSE; > > CString strName = m_strlist.GetNext(m_posCurrent); > BSTR bstrName = strName.AllocSysString(); > pbstrPageName = &bstrName; > return TRUE; >} > > >I then call this function from a simple test App (Class wizard >generated Class from TypeLib to wrap the IDispatch) and the following >code to exercise the function. > > > ASSERT(pDisp != NULL); > ISPageNames names; > names.AttachDispatch(pDisp); > BSTR bstrName; > names.Next(&bstrName); > CString strName = OLE2T(bstrName); > ::SysFreeString(bstrName); > > >The problem: >the BSTR returned by names.Next is valid but empty, even though tracing >through the code of SPageNames::Auto_Next shows that a valid, non-empty >string is being assigned. >By a valid BSTR, I mean that the assignment to strName passes off >without a hitch. Unfortunately the value of strname is an unhelpful >""; > >So, how should I go about passing back information in one of the >parameters of an automation method? > > >Giles Chamberlin >Softwright > -----From: "Siu-Wang Leung" Hi: If you code like the following: CString strName = m_strlist.GetNext(m_posCurrent); *pbstrPageName = strName.AllocSysString(); the code will work. Siu-Wang Leung -----From: Ian Pepper Hi Giles Try the following, BOOL SPageNames::Auto_Next(BSTR* pbstrPageName) { if(m_posCurrent == NULL) return FALSE; CString strName = m_strlist.GetNext(m_posCurrent); *pbstrPageName = strName.AllocSysString(); return TRUE; } The problem appears to be in the temporary varaiables assignment Ian ian@flexicom.ie -----From: "Michael J. Morel" ClassWizard provides you with an option to make a parameter of type = BSTR*. I'd use that, and not hand-edit anything. Here is a sample = function that passes a string back to VB via a parameter: #include ... BOOL CTestDoc::GetString(BSTR FAR* pbstr)=20 { USES_CONVERSION; SysReAllocString(pbstr, T2OLE("Hey!")); return TRUE; } In VB 4.0, my complex processing looks like this: Dim o As Object Dim s As String Dim b As Boolean Set o =3D CreateObject("Test.Document") b =3D o.GetString(s) MsgBox (s) This works for me. I'm VC 4.2, but that shouldn't matter. Mike Morel Mushroom Software Home of MFC For Yourself http://www.mushroomsoft.com/mushroom -----From: "Doug Brubacher" I think the problem with Giles' code is he is modifying the pointer pbstrPageName itself, rather then the address it is pointing at. I've being experimenting with Automation objects and I created a test method that does almost exactly what he wants, here's my implementation: STDMETHODIMP CBlamo::get_Item(long Index, BSTR* pbstr) { CString sString; sString.Format( "Index: %i", Index ); AfxMessageBox( sString ); if (pbstr == NULL) return E_POINTER; *pbstr = sString.AllocSysString(); return S_OK; } and the IDL definition: HRESULT Item([in] long Index, [out, retval] BSTR* pbstr); and here's a snippet from the calling function: BSTR bsString; ... hRes = pBlamo->get_Item( iIndex, &bsString ); if ( S_OK == hRes ) { CString sString( bsString ); plblString->SetWindowText( sString ); } ... I also do not call SysFreeString. I presume the destructor handles this automatically when the BSTR goes out of scope, at any rate VC++ does not report any leaks when I run the program. Regards Doug Brubacher