On 29/10/2010 7:28 AM, Steve Johnston wrote:
Hello Mark,
Thank you for responding to my query! I hope you don't mind that I am
replying directly to your email. I'm not sure what the proper protocol is.
It is best if replies stay on list for the benefit of others.
Your response makes sense, but I'm not sure why my application is not
returning the "...IDispatch implementation for the dual interface...".
Unfortunately, I'm not a COM expert. I looked in the source code, and there
is a function,
BOOL CFREDApp::GetDispatchIID( IID* pIID )
{
*pIID = IID_IDualFREDApp;
return TRUE;
}
which returns the IID of the dual interface. But I don't know if invoking a
method from the Python client ultimately calls this function to get the IID,
and ultimately, the dual interface.
The name looks misleading, but it will be returning the IID of the
vtable interface - IID_IDispatch is a fixed value.
Here is another short experiment from the Python Interactive window:
PythonWin 2.6.1 (r261:67517, Dec 4 2008, 16:51:00) [MSC v.1500 32 bit
(Intel)] on win32.
Portions Copyright 1994-2008 Mark Hammond - see 'Help/About PythonWin' for
further copyright information.
import win32com.client
app = win32com.client.Dispatch("FRED.Application")
app
<win32com.gen_py.FRED Type Library.IDualFREDApp instance at 0x16765696>
appdual =
app._oleobj_.QueryInterface("{7267D11E-5C4A-4C83-8766-19EBF0F87E85}")
Traceback (most recent call last):
File "<interactive input>", line 1, in<module>
TypeError: There is no interface object registered that supports this IID
That is expected - IID_IDualFREDApp is a custom IID which win32com knows
nothing about. win32com will so a QI for IID_IDispatch.
The IID in the QueryInterface call is the IID of the dual interface. I also
looked in my registry and there are several entries with that IID that look
reasonable. I can only assume that the interface is properly registered
since Visual Basic can successfully invoke methods from it.
VB is capable of dynamically using vtable interfaces which have a
typelibrary (which yours does). You need to track the code for when
IID_IDispatch is queried for.
Note I'm taking off on 2 weeks holiday tomorrow and may not be able to
reply while away...
Cheers,
Mark
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