Hi all,
I am having a problem that is identical to the one mentioned last year on
this list:
http://groups.google.com/group/sqlalchemy/browse_thread/thread/efd3993c94c8d162/37943cda02151f2b?lnk=gst&q=onupdate+inheritance#37943cda02151f2b
I have Engineer and Manager tables that are inheriting from an Employee
table using joined table inheritance. When I update one of the child
tables, I want the last_edited timestamp column on the Employee table to be
updated as well, but it is not updating. Mr. Bayer proposes the following:
"""
from sqlalchemy.orm import mapper as _mapper
from sqlalchemy.orm import MapperExtension
class MyExt(MapperExtension):
def before_update(self, mapper, connection, instance):
if hasattr(instance, '__before_update__'):
instance.__before_update__()
def mapper(*args, **kw):
kw['extension'] = MyExt()
return _mapper(*args, **kw)
just hide that code away someplace, and then any instance which
defines a method called __before_update__() will have it called before
update.
"""
I've done that step, but I don't understand what the next step is. I
thought that I would have to implement a __before_update__ method on my
Engineer and Manager classes, which would then call some method on Employee
using super. However, when I update my Engineer, it doesn't even look like
the __before_update__ method is being called. So I conclude that I'm doing
it wrong. Which instances should implement a __before_update__ method?
What should the __before_update__ method do?
Any advice would be extremely appreciated.
Thanks,
John
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