Notifying structures of editions

[Lukas Renggli]

> 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?

Exactly.

> 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.

Cheers,
Lukas

-- 
Lukas Renggli
http://www.lukas-renggli.ch