On Feb 28, 2006, at 11:25 AM, Marko Mikulicic wrote:
On 28.02.2006., at 16:09, Michael Bayer wrote:
it seems to me it would be "easier" to just map against the actual
SELECT statement that joins all three tables, and not use mapper
inheritance for this. youd have one Mapper that knows about the
Base class. then your MapperExtension would override
create_instance to provide Organization or Person objects....thats
the single point at which objects are instantiated. that way the
mapper would just deal with Base objects and not even know about
the subclasses.
This was the first idea that I tried, but didn't know how to fill
new instances from the row, without playing with internals that may
change between svn releases. Is there an example using
create_instance?
how many classes do you want to be able to add to this ? doing a
giant SELECT that outerjoins many tables, with only one being used
for each row, will perform very poorly.
anyway, create_instance is not too different from the append_result
you already figured out:
class MyExt(MapperExtension):
def create_instance(self, mapper, row, imap, class_):
if row['col1'] == 'foo':
return Organization(_mapper_nohistory=True)
else:
return Person(_mapper_nohistory=True)
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