Notifying structures of editions
renggli at iam.unibe.ch
Thu Nov 29 08:16:29 MET 2007
> When editing a structure, accessors are called via Magritte but there
> is no way for the structure to reinitialize itself before any accessor
> is called, or to re-establish its invariant after all accessors have
> been called.
It is possible to create a subclass of PREditCommand and override
#doExecute to trigger some postprocessing.
> I thought I'd wrap PRCommand>>doExecute with something like self
> structure willEdit and self structure didEdit, would that make sense?
> I think writing this helped me see a solution:
> - validation does the heavy parsing and stores result in (an adhoc
> subclass of) the edit command
> - executing the command stores parsed data in the structure and resets
> the final data
> - a lazy accessor for the final data builds it and ditches the
> parsed data
> hopefully that was clear… if you have suggestions…
Generally getting notified about events is a bit of a problem in Pier.
Several things (such as creating new structures, persistency, etc) are
quite, because this triggers events in rather clumsy ways. I once
rewrote part of this mess using announcements, which provides a
significant improvement over the current status but also breaks/
changes certain things. Unfortunately I lost the image, but if I have
time I probably redo it.
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