these are two general patterns, observer/listener and undo/redo (command-pattern), which have nothing to do with DB. i dont know about 2) DB-observers which would react on somebody else changing the DB, AFAIK that is possible on certain servers only, but the rest should be done independly on higher level than DB-stuff. read about Model-View-Controller.
On Tuesday 24 February 2009 15:00:28 paniq303 wrote: > Hi everyone, > > I am developing an offline music synthesizing and sequencing > application in Python, using the SQLite backend to store song data. > At the moment, I am using my own "object relational mapper" between > SQL and Python, which is fairly minimal. I feel compelled to use > SQLAlchemy, but there are two areas where I would like to assess my > options before I go forward and embed SQLAlchemy into my > application. > > 1) Is it possible/planned to connect signal handlers to database > changes? In my app, changing object properties will call connected > event handlers, which in turn refresh UI views. How could I do this > with SQLA? > > Can you think of another way to update the UI from DB changes? > Another way could be to have a hook listen to transactions and > generate journal records from which events can be signalled - this > would even enable multiple processes to handle events. Does that > sound more plausible? Is it possible? > > 2) I see that SQLA supports rollback for pending transactions, > which is a great feature. But as far as I understand, it is not > possible to rollback transactions that have already been committed > (undo). How would I go about and implement such a feature into my > application best, using SQLA as a backend? > > I understand that SQL is traditionally used in web services, where > event handling is virtually impossible and extensive undo/redo > functionality is rarely needed. But I believe it makes perfect > sense to use databases for document formats as well. > > Looking forward to your answer. > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~----------~----~----~----~------~----~------~--~---
