[AG-TECH] GetData() problem in wxPython shared application

[Thomas D. Uram]

First, a note:  if a non-existent key is passed to GetData, an empty string is returned. 
This causes variation in the evaluations that you did (len(d)>0 is false; d!=0 and d!=None 
are true).  You might instead simply use  'if d:'.  Initialization should not have any 
effect.  I'm curious about the junk you got back.

As to your question:  The application session in the venue doesn't clear out data when the 
last client leaves and, currently at least, can't be made to do so without some server 
side modifications.  A client could check to see if it is the last or first to join (using 
the GetParticipants call) and zero out the data; not exactly a great solution, but one 
that would work.  Also, there is not currently a method for removing data, so you can only 
zero it out.

Tom


Stephen Jeffrey wrote:
> Thanks Susanne. If I initialise the variable before
> calling GetData(), and then test using
> 
> if self.file:
> 
> it seems to work OK.
> 
> I now have another problem - the data does not get deleted
> from the application service when all copies of the application
> are terminated. The very first time the application is started,
> it reports there is no data stored, as it should. However if
> I terminate the application and then restart it, it reports
> that there is existing data. The only way to delete the data
> appears to be to delete the shared app from the venue client
> window, and then add the shared app again (using the Start
> Application Session option under the Venue menu in the venue
> client window). Is this normal behaviour, or do I have to
> somehow manually delete the data when the application terminates?
> 
> cheers
> steve
> 
> 
> Susanne Lefvert wrote:
> 
>> This works for me:
>>
>> -----------------------
>> self.file = None
>>
>> # Get current state
>> self.file = self.sharedAppClient.GetData("file")
>>
>> if self.file:
>>     # do stuff
>> else:
>>     print "data does not exist..."
>> ------------------------
>>
>> Which platform?
>>
>> Susanne
>>
>>
>> On Wed, 13 Apr 2005, Stephen Jeffrey wrote:
>>
>>
>>> Hi All,
>>>
>>> I am writing a shared application using wxPython. The application
>>> is to query if there is any shared data present when it starts.
>>> ie. if another copy of the application is already running and has
>>> sent some data using sharedAppClient.SetData(), when the second
>>> copy of the application starts it should obtain the data stored
>>> by the first copy.
>>>
>>> How can I query if there is any shared data already present?
>>> I have tried:
>>>
>>> d = self.sharedAppClient.GetData("data")
>>> if len(d) > 0:
>>>
>>> and other variations such as:
>>>
>>> d = self.sharedAppClient.GetData("data")
>>> if d != 0:
>>>
>>> and
>>>
>>> d = self.sharedAppClient.GetData("data")
>>> if d != None:
>>>
>>> but it appears as though GetData() is returning junk - when the
>>> first copy of the application starts there should not be
>>> any shared data present, but it returns non-zero data.
>>>
>>> Is there some way to overcome this, or do I have to somehow
>>> get the first instance of the application to "initialise"
>>> the shared data.
>>>
>>> cheers
>>> steve
>>>
>>> -- 
>>> Dr Stephen Jeffrey
>>> Advanced Computational Modelling Centre
>>> University of Queensland
>>> St. Lucia Queensland 4072 Australia
>>>
>>> Phone: +61 (7) 3365 6130
>>> Fax: +61 (7) 3365 6136
>>> Email: sjj at maths.uq.edu.au
>>> Web: http://www.acmc.uq.edu.au
>>>
>>>
> 
>