In fact we used to use metaclass way of handling this problem, but for
some unknown reason it was changed to monkey patching _as_declarative :|
Couple months ago I've read your post:
http://techspot.zzzeek.org/2011/05/17/magic-a-new-orm/
where there is a similar approach (classes generate relation
properties). I thought that in current SQLA it could be done also with
column properties, but if not it's fine, it's not a big of a deal...
just wanted to know if I can avoid this "hack".
Regards
Tomasz Jezierski
Tefnet
W dniu 21.09.2012 16:27, Michael Bayer pisze:
using a class there which replaces itself means you've developed a custom
creational pattern. A less hacky approach would be to subclass
DeclarativeMeta, and just pass it to your Base:
from sqlalchemy.ext.declarative import DeclarativeMeta
class TefnetMeta(DeclarativeMeta):
def __init__(cls, classname, bases, dict_):
for key, value in dict_.items():
if isinstance(value, TefProperty):
dict_[key] = value._config(cls, key)
super(TefnetMeta, cls).__init__(classname, bases, dict_)
Base = declarative_base(metaclass=TefnetMeta)
On Sep 21, 2012, at 10:17 AM, Tefnet Developers wrote:
My example is just the shortest code I could come up with to show a problem,
but in production it doesn't look like this.
We're using class inheritance, metaclass features etc, so changing it to
function is not an option for us :|
W dniu 21.09.2012 15:59, Michael Bayer pisze:
my immediate thought on that code is to replace TefProperty with a function,
since you are discarding TefProperty in any case:
def propInt():
return sa.Column(key, Integer)
not sure how the previous Extension version of the code did this differently,
this is really a class creational pattern.
On Sep 21, 2012, at 2:59 AM, Tefnet Developers wrote:
Hi,
we are trying to migrate our old *Extension based SQLA code to new - event
based.
We also have class based properties that we want to keep. With old SQLA we have had to
monkey-patch _as_declarative function to populate our properties. I wonder if it is
possible to avoid doing it with events? The only close one we found is
"mapper_configured", but I'm afraid it is executed too late. Anyway... I've
prepared some short example code. If you could take a look and advise if/how it can be
done...
To check out where is the problem change USE_EVENT value from True to False.
https://gist.github.com/3757273
Regards,
Tomasz Jezierski
Tefnet
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