Support pre/post-save and pre/post-update

[soderluk]

Any thoughts on supporting some kind of pre-save, and pre-update (and why not pre/post-delete) functionality? Either as functions to override, or events?

As a use case, I've got created_at and updated_at datetimes for my models. Setting the default value works, but e.g. when updating a model, I'd like to automatically set the updated_at to current datetime. Now I have to manually add the timestamp to the model for it to update.

Of course I can make a base class of my own, and override the save and update functions, but it seems a bit overkill. Also a lot of the libraries out there has some kind of functionality for these kind of situations.

Thoughts?

[collerek]

Yep, sounds like a good idea.

Probably something like a decorator registering event/signal for a given method.

Alternative or maybe additional functionality might be adding some kind of parameters like 'on_update' and 'on_delete'.

[collerek]

Should be closed in #66