[SQLObject] Inheritance strangeness

[<ab...@ne...>]

I've discovered what seems to be a bug in sqlobject class inheritance.

An inherited class whose parent defines a foreign key, can only use that =
foreign
key/pointer if they themselves define a data attribute.  If the inherited=
 class
does not contribute a new data attribute, attempting to use the foreign k=
ey
(which is defined by the parent) will generate an attribute error.

P.S. You need to grab the latest source from the subversion repository in=
 order
to get the InheritableSQLObject class. Release 0.6.1 doesn't come with it=
.

#----------------------------------------------
from sqlobject import *
from sqlobject.inheritance import InheritableSQLObject
from sqlobject.sqlite import builder; SQLiteConnection =3D builder()
conn =3D SQLiteConnection('persontest3.db', debug=3DFalse)

class Cubicle(SQLObject):
    _connection =3D conn
    location =3D StringCol()
    occupiedby =3D ForeignKey('Person', default=3DNone) # and subclasses

class Person(InheritableSQLObject):
    _connection =3D conn
    cubicle =3D ForeignKey('Cubicle')

class Employee(Person):
    _connection =3D conn
    _inheritable =3D False                     # comment this line to sol=
ve bug OR
    #position =3D StringCol(default=3D'Chief')   # uncomment this line to=
 solve bug
 =20
# tests   =20
Cubicle.dropTable(True)
Cubicle.createTable()

Person.dropTable(True)
Person.createTable()

Employee.dropTable(True)
Employee.createTable()

c =3D Cubicle(location=3D'first floor')
c.occupiedby =3D Employee(cubicle=3Dc)

# The following will crash with the error
# 'Employee' object has no attribute '_SO_val_cubicleID'

print 'c.occupiedby.cubicle', c.occupiedby.cubicle    # BOOM!

#----------------------------------------------

Admittedly, most people using inherited classes want to define extra attr=
ibutes
- that's usually the whole point of an inherited class.  So they would no=
t run
into this problem.  However in my situation not all my inherited classes =
define
extra attributes (e.g. they instead have different behaviour etc.) so it =
is a
real problem for me.

-Andy Bulka
www.atug.com/andypatterns



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