tim at sumeru.stanford.edu
Tue Jan 27 01:30:57 UTC 2004
On Jan 26, 2004, at 1:38 AM, Andreas Raab wrote:
> That's why I'm saying putting the resource creation inside the ensured
> doesn't give you anything, and that's why you don't need explicit
> guards nor
> stub methods in UndefinedObject. You simply can't handle failures that
> from resource creation contained inside some ensured block that should
> the release of that resource.
Not quite completely true, though it would require a change in the
resource allocation behaviour to be clean.
a) one could simply do the ugly thing and make UndefinedObject respond
to the resource release message (yuck)
b) one could return an instance of FailedResourceAllocationDoohickey
rather than nil when the file open fails and provide it with protocol
to do various useful things. Like maybe retry under some situations,
release 'cleanly' and so on.
With b) we would anticipate an exception from the "do stuff" part of
the ensured block which would then unwind and the 'file' would handle
#close by doing nothing much. Is this a good pattern? Not sure right
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