On Sep 21, 2012, at 10:57 AM, Tefnet Developers wrote: > 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".
you can use that approach, it makes use of the "mapper_configured" event, which for some reason you're saying you can't use. there's other events to use, but often there are other issues that get in the way when you try to alter mappings within them. You can try "instrument_class": http://docs.sqlalchemy.org/en/rel_0_7/orm/events.html#sqlalchemy.orm.events.MapperEvents.instrument_class but the fact that my blog post doesn't use it might indicate I hit problems when trying to use that one. > > 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 >>>>> >>>>> -- >>>>> You received this message because you are subscribed to the Google Groups >>>>> "sqlalchemy" group. >>>>> To post to this group, send email to sqlalchemy@googlegroups.com. >>>>> To unsubscribe from this group, send email to >>>>> sqlalchemy+unsubscr...@googlegroups.com. >>>>> For more options, visit this group at >>>>> http://groups.google.com/group/sqlalchemy?hl=en. >>>>> >>> -- >>> You received this message because you are subscribed to the Google Groups >>> "sqlalchemy" group. >>> To post to this group, send email to sqlalchemy@googlegroups.com. >>> To unsubscribe from this group, send email to >>> sqlalchemy+unsubscr...@googlegroups.com. >>> For more options, visit this group at >>> http://groups.google.com/group/sqlalchemy?hl=en. >>> > > -- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To post to this group, send email to sqlalchemy@googlegroups.com. > To unsubscribe from this group, send email to > sqlalchemy+unsubscr...@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/sqlalchemy?hl=en. > -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
