Re: [SQLObject] Saving a rol with a derivative atribute

[Oleg B. <ph...@ph...>]

Hi!

On Wed, Sep 11, 2013 at 10:25:31AM -0300, Georgio Barbosa <geo...@gm...> wrote:
> I would like to know if it is possible to create a model class with a
> default attribute derived from another.
> 
> An example:
> 
> class Post(SQLObject):
> *title = StringCol()*
> content = StringCol()
> create_time = DateTimeCol(default=datetime.now)
> tags = RelatedJoin('Tag')
> author = ForeignKey('Author')
> *slug = StringCol(default=title.replace(" ", "-"))*

   It is possible but in a rather complex non-obvious way. You have to
use events (signals); unfortunately that gem of SQLObject is
underdocumented (to say mildly), so you need to consult the code.
   See http://sqlobject.org/SQLObject.html#events-signals for the
starting point. Read events.py and lookup main.py to see how signals are
sent and how SQLObject uses returned values.
   You need to catch RowCreateSignal and RowUpdateSignal -- they are
sent before INSERT and UPDATE correspondingly -- and update values to
your need in your signal handlers.

   It would be great if after you learn the details of events you sent a
patch to improve documentation. Or any other patch -- code,
documentation, tests -- any help will be greatly appreciated.

Oleg.
-- 
     Oleg Broytman            http://phdru.name/            ph...@ph...
           Programmers don't die, they just GOSUB without RETURN.