Need help on call COM method from VBScript.

**sm_ch** · July 13th, 2004, 01:53 AM

I have developed a COM DLL under VC++ 6.0. The project is created by COM wizard.The interface's name is ISMA. Then I add a method to it.The code is
interface ISMA : IDispatch
{
[id(1), helpstring("method IFInitInterface")] HRESULT IFInitInterface(DWORD dwCodeProtocol, DWORD dwDriverProtocol, LPCTSTR pDriverParam);
};

STDMETHODIMP CSMA::IFInitInterface(DWORD dwCodeProtocol, DWORD dwDriverProtocol, LPCTSTR pDriverParam)
{
// TODO: Add your implementation code here
return m_impClass.Test();
return S_OK;
}
--------------------------

<%
set obj=Server.CreateObject("SMACOM.SMA.1")
%>
<HTML>
<%
i = obj.IFInitInterface(0,0,"1")
%>
</HTML>

The error is IFInitInterface is not a VBScript supported Automation type.
Error code is 800a01ca.

Thanks a lot.

**jwalto1** · July 13th, 2004, 02:57 PM

Hi sm_ch,

Since you are using vb script, everything needs to be a VARIANT.

Return HRESULTs.

To return a value to a client, you need a [out, retval] parameter.

Use BSTRs instead of LPCTSTR.

Note that VBScript requires VARIANTs - if you have a smart Automation aware language such as VB or Visual Java, you could actually pass BSTR*'s as parameters/return values.

Something similar to below should work...

See http://msdn.microsoft.com/library/de...ion_topics.asp and http://msdn.microsoft.com/library/de...chap7_5alv.asp

See also http://msdn.microsoft.com/library/de...chap6_7zdz.asp for the VARIANT structure.

Jeff

Code:

[id(1), helpstring("method Test")] HRESULT
Test( [in] VARIANT* param, [out, retval] VARIANT* retval );

And

Code:

STDMETHODIMP CTest::Test(VARIANT* param, VARIANT* retval)
{
    if( NULL == param || param->vt != VT_BSTR )
    {
        return E_INVALIDARG;
    }

    if( NULL == retval || retval->vt != VT_BSTR )
    {
        return E_INVALIDARG;
    }

    HRESULT hr = SysFreeString( *retval );

    if( FAILED( hr) )
    {
        return hr;
    }

    USES_CONVERSION;
    LPCTSTR szParam = OLE2T(param);

    // tinker with szParam

    *retval = SysAllocString( szParam );

    if( NULL == *retval )
    {
        return E_MEMORY;
    }

    return S_OK;
}

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