I am trying to my my joined inheritance code clearer, for the dynamic
generation of sa classes and tried to do something like this:
class InheritMixin(object):
@declared_attr
def __tablename__(cls):
return cls.__name__
@declared_attr
def id(cls):
if cls.__name__ == 'Object':
return Column(Integer, primary_key = True)
else:
print 'in id: ', cls.__name__, cls.__bases__[0].__name__
return Column(Integer,
ForeignKey(cls.__bases__[0].__name__ + '.id'), primary_key = True)
@declared_attr
def __mapper_args__(cls):
if cls.__name__ == 'Object':
return {'polymorphic_on': 'discriminator'}
else:
print 'in mapper_args: ', cls.__name__,
cls.__bases__[0].__name__
return {'polymorphic_identity': cls.__name__,
'inherit_condition': (cls.id ==
cls.__bases__[0].id)}
Object = type('Object', (Base, InheritMixin), clsdict)
Where Object should be the (not necessarily direct) baseclass of all
inheriting classes. However I get errors: "Mapper Mapper|person|person
could not assemble any primary key columns for mapped table 'Join
object on Object(65389120) and person(65428224)' " etc ..
I noticed that the method __mapper_args__(cls) is always called before
id(cls) (which is never called, probably due to the error.
Is there some way to fix this, while keeping the inheritance code in a
mixin?
Also, is there a way to add the discriminator column to the mixin (if
i just directly add it to the declaration, this gave another maybe
related error)?
Cheers, Lars
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