[wtp-dev] Proposed new pattern for managed models (was "Re: Scary code")

[David M Williams <david_williams@xxxxxxxxxx>]

Naci Dai wrote .... 
>There is something that makes me uneasy about the
following code...
>
 >core = StructureEdit.getStructureEditForRead(projects[i]);
>....
>some stufff
>...
>core.dispose();
>
>This is very open to making mistakes (i.e unbalanced dispose). I do
not have 
>an answer to an alternative, try-finally is a clumsy
workaround, 
>but I have a feeling this bug will also be a pattern.

I'm not sure our SSE ModelManager is the only reason for
this pattern, 
but it is one. 

The model provided is a "shared resource" so,
it is appropriate for clients to 
be required to use a try {} finally{} pattern to ensure
proper acquisition and 
release. But ... it is admittedly a problem area and often
prone to bugs. 

To help address this, part of our proposed API change
(for next milestone) will be to move to 
a pattern something like 

connect(requester, IPath)

model = getModel(IPath)

disconnect(requester, IPath). 

A try/finally pattern will still be required (and is still
appropriate) ... but 
1) it is similar to the base eclipse's 
pattern in IFileBufferManager ... so maybe more familar
to Eclipse programmers? (or, is 
at least one problematic pattern instead of two :),  and
2) the presense of 'requester' on the call will allow
for improved debugging messages 
(eventually) [thanks to Jason Sholl for this suggestion]

Thought I'd post these ideas here now, instead of waiting
till whole design change 
documented, in case there was any wtp developer comment
or implications we
should be aware of. 

Thanks for the discussion.