[ pywin32-Bugs-2726657 ] getting PyIUnknown for a known return type‏

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Bugs item #2726657, was opened at 2009-04-02 23:01
Message generated for change (Comment added) made by mhammond
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Category: com
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Patricio Stegmann (kpoman)
Assigned to: Nobody/Anonymous (nobody)
Summary: getting PyIUnknown for a known return type‏

Initial Comment:
Hello all,

I am getting a strange behaviour for a generated clsid:

class IAcquisitionDevice(DispatchBaseClass):

    # SOME CODE STRIPPED HERE

    # Result is of type IAcquisitionDeviceInfo
    def EnumerateDevices(self):
        return self._ApplyTypes_(1610743823, 1, (8201, 0), (), u'EnumerateDevices', '{7ED03FE9-4DCC-4F5D-BDF8-4D4D22C1FA10}',)

    def GetNumberOfDevices(self):
        return self._oleobj_.InvokeTypes(1610743822, LCID, 1, (3, 0), (),)

    # SOME CODE STRIPPED HERE


# THEN SOME LINES LATER
class IAcquisitionDeviceInfo(DispatchBaseClass):
    CLSID = IID('{7ED03FE9-4DCC-4F5D-BDF8-4D4D22C1FA10}')
    coclass_clsid = IID('{DDD89560-8B0E-4D6F-9BDF-7E14068C1DEB}')

    _prop_map_get_ = {
        "Properties": (1610743809, 2, (8, 0), (), "Properties", None),
        "SerialNumber": (1610743808, 2, (8, 0), (), "SerialNumber", None),
    }
    _prop_map_put_ = {
    }




I saved all this on a mk4 file.

Then I perform some tests:

>>> import mk4
>>> dev = mk4.AcquisitionDevice()
>>> print dev.GetNumberOfDevices()
1
>>> print dev.EnumerateDevices()
(<PyIUnknown at 0x00BCB4C0 with obj at 0x0509FF90>,)
>>>



I dont know why I am getting a PyIUnknown if it should now I am returning IAcquisitionDevice object !
I guess there is some error somewhere and I really need to fix it. From that ActiveX documentation I see this:

void  EnumerateDevices (AcquisitionDeviceInfo infos[])
  enumerate all connected acquisition devices 


So it should return an array of infos and not only one info (this array contains infos for all the different compatible devices).
So somehow the python cache file got wrongly generated. How can I fix this please ? How to declare it should be an array of deviceinfos instead of a single deviceinfo ?


Thank you all for any help,

Patricio

----------------------------------------------------------------------

>Comment By: Mark Hammond (mhammond)
Date: 2009-04-06 21:58

Message:
Do you have any information about the API exposed by this object.  Looking
at:

# Result is of type IAcquisitionDeviceInfo
def EnumerateDevices(self):
return self._ApplyTypes_(1610743823, 1, (8201, 0), (),
u'EnumerateDevices', '{7ED03FE9-4DCC-4F5D-BDF8-4D4D22C1FA10}',)

It seems something (maybe pywin32, maybe the object) is confused about the
enumeration.  A function named 'EnumerateDevices' would be expected to
return a list/enum of IAcquisitionDeviceInfo's, not an
IAcquisitionDeviceInfo directly, and I suspect this is the root of the
problem.  To confirm, adding a print to the __init__ of
IAcquisitionDeviceInfo might tell you if we are trying to create such an
object, but failing (presumably as we have an enum)

----------------------------------------------------------------------

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