Re: [python-win32] Passing Nothing into ReferencesEvents - resolved, however can't bind events

Mark Hammond Thu, 15 Oct 2009 17:05:00 -0700

On 15/10/2009 10:50 PM, shivisi wrote:

Passing Application.VBE.Events.ReferencesEvents(None) works (at least at this 
point).
However, when I try to bind to an event class, I get the error below.
Any assistance, debugging suggestions, would be greatly appreciated.
Thanks.


# Code
from win32com.client import Dispatch, DispatchWithEvents, getevents

class RefEvents:
     def OnItemAdded(self,ref):
         print '--Event - Reference added'
     def OnItemRemoved(self,ref):
         print '--Event - Reference removed'

acc=Dispatch('Access.Application')
acc.Visible=True
refsEvents=DispatchWithEvents(acc.VBE.Events.ReferencesEvents(None),RefEvents)

See the docstring for DispatchWithEvents - you probably want somethingcloser to:


acc = DispatchWithEvents('Access.Application', RefEvents)
acc.Visible = True
win32com.PumpMessages() # sit here doing nothing but waiting for events...

Cheers,

Mark

#-----------------------------------------------------------------------------
Traceback (most recent call last):
   File "<interactive input>", line 1, in<module>
   File "C:\Python26\lib\site-packages\win32com\client\__init__.py", line 245, 
in DispatchWithEvents
     disp = Dispatch(clsid)
   File "C:\Python26\lib\site-packages\win32com\client\__init__.py", line 96, 
in Dispatch
     return __WrapDispatch(dispatch, userName, resultCLSID, typeinfo, 
clsctx=clsctx)
   File "C:\Python26\lib\site-packages\win32com\client\__init__.py", line 43, 
in __WrapDispatch
     return dynamic.Dispatch(dispatch, userName, WrapperClass, typeinfo, 
clsctx=clsctx)
   File "C:\Python26\lib\site-packages\win32com\client\dynamic.py", line 118, 
in Dispatch
     typeinfo = IDispatch.GetTypeInfo()
AttributeError: 'PyIUnknown' object has no attribute 'GetTypeInfo'
#-----------------------------------------------------------------------------

acc.VBE.Events.ReferencesEvents

<bound method Events.ReferencesEvents of<win32com.gen_py.Microsoft Visual Basic for 
Applications Extensibility 5.3.Events instance at 0x17466752>>

acc.VBE.Events.ReferencesEvents(None)

<PyIUnknown at 0x0102CFF8 with obj at 0x00190AEC>


Original message:

I am writing a COM addin, and attempting to trap the ItemAdded/ItemRemoved 
event in the following object:
Application.VBE.Events.ReferencesEvents
which is retrieved by passing Nothing as a paramter:
Application.VBE.Events.ReferencesEvents(Nothing)

Tim Golden wrote in the following post 
(http://mail.python.org/pipermail/python-win32/2009-February/008826.html) that 
pythoncom.Empty can be used for Nothing. However, when trying this:

try:
     self.comRefevents=self.app.VBE.Events.ReferencesEvents(pythoncom.Empty)
except pythoncom.com_error, (hr, msg, exc, arg):
     print "The call failed with code %d: %s" % (hr, msg)
         if exc is None:
             print "There is no extended error information"
         else:
             wcode, source, text, helpFile, helpId, scode = exc
             print "The source of the error is", source
             print "The error message is", text
             print "More info can be found in %s (id=%d)" % (helpFile, helpId)

I get back the following (the same as if I had passed no arguments at all):

The call failed with code -2147352561: Parameter not optional.
There is no extended error information

Eric Lippert states in his blog 
(http://blogs.msdn.com/ericlippert/archive/2004/07/14/183241.aspx):

A common alternative to passing a missing argument is to pass Nothing, Null, or 
Empty in VBScript,
null or undefined in JScript.  Null and null pass VT_NULL, Empty and undefined 
pass VT_EMPTY, and
Nothing passes a VT_DISPATCH with no value dispatch object pointer.

It would seem that VB's Nothing and Empty are two different things.

If I try passing pythoncom.VT_DISPATCH, then I get the following traceback:

-----------------------------------------------------------------------------------------------------------
Traceback (most recent call last):
   File "C:\Python26\lib\site-packages\win32com\universal.py", line 177, in 
dispatch
     retVal = ob._InvokeEx_(meth.dispid, 0, meth.invkind, args, None, None)
   File "C:\Python26\lib\site-packages\win32com\server\policy.py", line 324, in 
_InvokeEx_
     return self._invokeex_(dispid, lcid, wFlags, args, kwargs, serviceProvider)
   File "C:\Python26\lib\site-packages\win32com\server\policy.py", line 649, in 
_invokeex_
     return DesignatedWrapPolicy._invokeex_( self, dispid, lcid, wFlags, args, 
kwArgs, serviceProvider)
   File "C:\Python26\lib\site-packages\win32com\server\policy.py", line 585, in 
_invokeex_
     return func(*args)
   File "C:\Documents and Settings\ABG7\My 
Documents\Zevi\Python-COMAddin\VBACodeRepository.py", line 104, in OnConnection
     
self.comRefevents=self.app.VBE.Events.ReferencesEvents(pythoncom.VT_DISPATCH)
   File 
"C:\Python26\lib\site-packages\win32com\gen_py\0002E157-0000-0000-C000-000000000046x0x5x3.py",
 line 145, in ReferencesEvents
     ret = self._oleobj_.InvokeTypes(202, LCID, 2, (13, 0), ((13, 1),),VBProject
TypeError: The Python instance can not be converted to a COM object
pythoncom error: Unexpected gateway error

Traceback (most recent call last):
   File "C:\Python26\lib\site-packages\win32com\universal.py", line 177, in 
dispatch
     retVal = ob._InvokeEx_(meth.dispid, 0, meth.invkind, args, None, None)
   File "C:\Python26\lib\site-packages\win32com\server\policy.py", line 324, in 
_InvokeEx_
     return self._invokeex_(dispid, lcid, wFlags, args, kwargs, serviceProvider)
   File "C:\Python26\lib\site-packages\win32com\server\policy.py", line 649, in 
_invokeex_
     return DesignatedWrapPolicy._invokeex_( self, dispid, lcid, wFlags, args, 
kwArgs, serviceProvider)
   File "C:\Python26\lib\site-packages\win32com\server\policy.py", line 585, in 
_invokeex_
     return func(*args)
   File "C:\Documents and Settings\ABG7\My 
Documents\Python-COMAddin\VBACodeRepository.py", line 104, in OnConnection
     
self.comRefevents=self.app.VBE.Events.ReferencesEvents(pythoncom.VT_DISPATCH)
   File 
"C:\Python26\lib\site-packages\win32com\gen_py\0002E157-0000-0000-C000-000000000046x0x5x3.py",
 line 145, in ReferencesEvents
     ret = self._oleobj_.InvokeTypes(202, LCID, 2, (13, 0), ((13, 1),),VBProject
TypeError: The Python instance can not be converted to a COM object


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Re: [python-win32] Passing Nothing into ReferencesEvents - resolved, however can't bind events

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