Discussion group for comtypes users ()

Thomas Heller | 8 Jan 2009 18:54

Re: Problem with AutoCAD

Kelie schrieb:
> Ronan,
> 
> There is a cast function. But the syntax isn't much shorter.
> 
> import comtypes
> import comtypes.gen.AutoCAD as ACAD
> 
> app = comtypes.client.GetActiveObject("AutoCAD.Application")
> obj = app.ActiveDocument.ModelSpace(1)
> 
> #Assume this obj is a block
> block = comtypes.cast(obj, comtypes.POINTER(ACAD.IAcadBlockReference))
> # I hope this would work
> # block = comtypes.cast(obj, ACAD.IAcadBlockReference)
> 
> print "Layer name: %s" % block.Layer
> print "Color: %d" % block.Color
> print block.InsertionPoint
> print block.XScaleFactor
> 
> But I'm getting error when trying to access various block properties. See output
> below. Apparently it was OK to access the "Layer" and "Color" properties. Don't
> know why. Waiting for Thomas...

I haven't followed this thread so I do not really know what
all this is about.

Anyway, you should NOT use 'cast' with COM object pointers. Last,
but not least, 'cast' doesn't handle the COM reference count correctly.

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Kelie | 8 Jan 2009 23:50

Re: Problem with AutoCAD

Thomas Heller <theller <at> ...> writes:
> 
> Anyway, you should NOT use 'cast' with COM object pointers. Last,
> but not least, 'cast' doesn't handle the COM reference count correctly.
> 
> Please use 'QueryInterface' with them, like so:
> 
> block = obj.QueryInterface(ACAD.IAcadBlockReference)
> 

Thanks Thomas. I'm getting an error using QueryInterface.

> "C:\Python25\pythonw.exe"  "C:\Python25\codes\autocad\temp\cast_test.py" 
Traceback (most recent call last):
  File "C:\Python25\codes\autocad\temp\cast_test.py", line 9, in <module>
    block = obj.QueryInterface(ACAD.IAcadBlockReference)
  File "C:\Python25\Lib\site-packages\comtypes\__init__.py", line 1069, in
QueryInterface
    self.__com_QueryInterface(byref(iid), byref(p))
_ctypes.COMError: (-2147467262, 'No such interface supported', (None, None,
None, 0, None))

This is what I got from shell:
>>> import comtypes.gen.AutoCAD as ACAD
>>> ACAD.IAcadBlockReference
<class
'comtypes.gen._851A4561_F4EC_4631_9B0C_E7DC407512C9_0_1_0.IAcadBlockReference'>

------------------------------------------------------------------------------
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Thomas Heller | 9 Jan 2009 19:19

Re: Problem with AutoCAD

Kelie schrieb:
> Thomas Heller <theller <at> ...> writes:
>> 
>> Anyway, you should NOT use 'cast' with COM object pointers. Last,
>> but not least, 'cast' doesn't handle the COM reference count correctly.
>> 
>> Please use 'QueryInterface' with them, like so:
>> 
>> block = obj.QueryInterface(ACAD.IAcadBlockReference)
>> 
> 
> Thanks Thomas. I'm getting an error using QueryInterface.
> 
>> "C:\Python25\pythonw.exe"  "C:\Python25\codes\autocad\temp\cast_test.py" 
> Traceback (most recent call last):
>   File "C:\Python25\codes\autocad\temp\cast_test.py", line 9, in <module>
>     block = obj.QueryInterface(ACAD.IAcadBlockReference)
>   File "C:\Python25\Lib\site-packages\comtypes\__init__.py", line 1069, in
> QueryInterface
>     self.__com_QueryInterface(byref(iid), byref(p))
> _ctypes.COMError: (-2147467262, 'No such interface supported', (None, None,
> None, 0, None))

I guess this means, well, that the interface is not supported.

BTW:  Sometimes, interfaces ARE supported by COM objects but cannot
be marshalled across process boundaries.  You also get the above error
in this case.

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