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From: Gregor H. <gh...@gr...> - 2011-02-14 09:18:58
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Am Mon, 14 Feb 2011 11:38:57 +0300
schrieb Oleg Broytman <ph...@ph...>:
> On Mon, Feb 14, 2011 at 11:26:47AM +0300, Oleg Broytman wrote:
> > On Mon, Feb 14, 2011 at 09:08:57AM +0100, Daniel Fetchinson wrote:
> > > >> Now that we are at it I was wondering whether
> > > >> something similar could be adopted for tables too. The order
> > > >> in which the tables are defined, class table1( SQLObject ),
> > > >> class table2( SQLObject ), etc, etc, could also be significant
> > > >> and one might want to remember this ordering. And since there
> > > >> is all sorts of metaclass trickery involved with class
> > > >> creation, maybe the ordering could be stored.
> > > >>
> > > >> What do you think?
> > > >
> > > > Yes, it could be done in a metaclass or in the constructor.
> > >
> > > As far as I can see declarative.DeclarativeMeta is the place to
> > > look. I'll try to come up with something.
> >
> > DeclarativeMeta is a generic metaclass. SQLObject-specific
> > metaclass should become its descendant. I suppose you don't need to
> > have .creationOrder attribute in all classes (sqlmeta?)
> > If you only need .creationOrder in SQLObject classes (tables)
> > it's enough to set it in __init__, right before testing for
> > _SO_fetch_no_create.
> > Actually I started to think .creationOrder if the tables is not
> > that interesting because it depends on the order of import. The
> > order of columns is more interesting and more stable.
>
> Oops, dammit, a classical wrong way of thinking. __init__ is about
> creating *rows*, and you certainly is thinking about *classes*. So the
> only right way to go is a metaclass.
>
I've done a similar thing for other classes (not SQLObject) with
DeklaraticeMeta from SQLObject:
classnr = 0
class Base(object):
__metaclass__ = declarative.DeclarativeMeta
def __classinit__(cls, newattrs):
log.debug("%s.__classinit__" % cls)
global classnr
classnr = classnr + 1
--
Greg
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