Re: [SQLObject] two beginner's questions

[Luke O. <lu...@me...>]

> 2. is there a way to control redundancy in the following example:
>
> class test1 (SQLObject):
>   _columns = [StringCol("lang", lenght=2, default='en'),
>               IntCol("someOtherStuffHere")]
>
> class test2 (SQLObject):
>   _columns = [StringCol("lang", lenght=2, default='en'),
>               StringCol("differentStuffThanInTest1")]
>
> I would like to decide only once how to represent a language in the
> DBMS and use this consistently in various class definitions.
>
> I unsuccessfully tried to define a StringCol object, langCol,

I know we're getting caught up in all sorts of things tangentially
related (I'm currently in the midst of figuring out why making an
abstract class with columns and then saying _columns = Super._columns
+ [] doesn't quite work...)

But there is a somewhat simple non-SQLObject-inheritance-based way to
get what you want, without the foreign table suggested by Frank.
Rather than define a StringCol object, define a LangCol *class* which
is a subclass of StringCol. Something like this ought to work:

class LangCol(StringCol):
    def __init__(self, **kw):
        kw['length'] = 2
        kw['default'] = 'en'
        StringCol.__init__(self, 'lang', **kw)

Yep, just tested this out. Actually, just tested my example above with
Super._columns, and it works too! (Using 3.0. All classes currently
have a problem with CVS checked out 10 minutes ago, which was
throwing me off.)


So. To elaborate. You can either define your common column type as a
subclass of Col (or StringCol, etc). Or you can use SQLObject
inheritance with a structure like:

class AbstractObject(SQLObject):
    _columns = StringCol('lang')

class Z(AbstractObject):
    _columns = AbstractObject._columns + [StringCol('nother')]

class Y(AbstractObject):
    _columns = AbstractObject._columns + [StringCol('further')]

And all of this actually seems to work in SQLObject 0.3, tested using
DBMConnection. Wow. What do you say to that, Nick? :)

- Luke

P.S. I'm still tracking down the problem with CVS, but it initially
appears to be related to _SO_plainSetters and addColumn. Just a heads
up, Ian.