passing a struct to a IDispatch method

Question

In a third party COM Module I have to pass a struct to a Method.

The important parts of the IDL definition look like this:

interface ITheirInterface : IDispatch {
    [id(0x0000012d)]
    HRESULT TheirMethod([in] TheirStruct Attributes);
};

struct TheirStruct {
    BSTR TheirFieldA;
    BSTR TheirFieldB;
} TheirStruct;

I how do I call the method from C++ using the ATL?

CComPtr<IDispatch> comPtr; 
comPtr.CoCreateInstance(L"theirModule.TheirCoClass");
CComVariant returnValue;
CComVariant attribute= I_DO_NOT_KNOW_WHAT_TO_PLACE_HERE;
comPtr.Invoke1(T2COLE(L"TheirMethod"),&attribute,&returnValue);

score 3 · Accepted Answer · answered Jan 19 '11 at 23:30

3

COM automation support for structures is very weak, CComVariant doesn't support it directly. You need to use IRecordInfo and create a variant of type VT_RECORD. Obtain the IRecordInfo interface pointer from GetRecordInfoFromTypeInfo or GetRecordInfoFromGuids. Good luck.

answered Jan 19 '11 at 23:30

Hans Passant

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Googling a bit, I found a german article in the MSDN http://msdn.microsoft.com/de-de/library/bb979533.aspx I think, the last listing does what you where explaining. Am I right? – Jan Jan 20 '11 at 00:47
Yup, note the call to GetRecordInfoFromGuids. – Hans Passant Jan 20 '11 at 00:55

passing a struct to a IDispatch method

1 Answers1