I don't know what "@validates hangs a marker of the method that
mapper() uses when it instruments the class" means. I guess my
question now becomes: How do I add the event.listens_for descriptor to
the class, since i do not have a class declaration in the traditional
sense?
On Apr 15, 4:29 pm, Michael Bayer <mike...@zzzcomputing.com> wrote:
> @validates hangs a marker of the method that mapper() uses when it
> instruments the class, so if the class is already mapped then that train has
> left the station. Taking a cab instead, you can just add the attribute
> event directly:
>
> @event.listens_for(Positive.value, "set")
> def checkvalue(target, value, oldvalue, initiator)
> assert value > 0
>
> if you want to return a new, mutated value then add retval=True to
> listens_for().
>
> On Apr 15, 2012, at 8:22 AM, lars van gemerden wrote:
>
>
>
>
>
>
>
> > Hi,
>
> > I need a way to dynamically add a validates method to a already
> > created sqla class.
>
> > In a normal class declaration you can add a validator by:
>
> > class Positive(Base):
> > __tablename__ = "positives"
> > value = Column(Integer)
>
> > def checkvalue(self, name, value):
> > assert value > 0
> > return value
> > validates("value")(checkvalue)
>
> > However if you get the class dynamically:
>
> > Positive = type("Positive", (Base,), dict(__tablename__ =
> > "positives", value = Column(Integer)))
>
> > I can't figure out how to add the validator, either in the type() call
> > or afterwards.
>
> > Cheers, Lars
>
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