[Modeling-users] inheritance and relations confusion

[Mario R. <ma...@ru...>]

Hi,

I have an entity (B) inheriting from another (A), with the
constraint that any instance of either must be related
to one instance of B. The corresponding model is therefore:

model.entities = [
   Entity('A', ...),
   Entity('B', parent='A', ...),
]

model.associations=[
   # A is always related to a B
    Association('A','B',
     relations=['b','as'],
     multiplicity=[ [1,1], [0,None] ],
     delete=['nullify','deny'],
     keys=['fkBId','id'],
   ),
]

I can create the instances and rels in the expected way,
but when I come to delete them, there is a problem:
I try to get to the b for the a in question, to nullify the
relation (respecting the "deny" delete rule). Thus I do:

 > > > a = ec.fetch('A',qualifier='...',isDeep=1)[0] # gives correct a
 > > > b = a.getB()
 > > > b
.<pympack.A.A instance at 0x95ba60>
 > > > for related_a in b.getAs():
               b.removeFromAs(related_a)
Traceback (most recent call last):
     for related_a in b.getAs():
AttributeError: A instance has no attribute 'getAs'

Thus, he insists that the b instance is of type A,
and does not find the getAs() rel-method on it (but the
id and other b-only non-rel attributes are correctly
present!).

But, removing known objects "explicitly", with :

     a.removeObjectFromBothSidesOfRelationshipWithKey(b,'b')

as many times as necessary (for each a related to this b) works
just fine.

Any enlightenment?

Cheers, mario

ps: ah, but when did relations ever behave nicely when inheritance is 
involved ;-?