[Sqlalchemy-users] can't assign to a polymorphic property

[Vladimir Iliev]

hi,
i want to assign details or assemblies to the 'slave' property of the
spec lines but i can't.
what's wrong with my mapping ?




from sqlalchemy import *
from datetime import datetime


metadata = BoundMetaData('sqlite://', echo=False)


products_table = Table('products', metadata,
   Column('product_id', Integer, primary_key=True),
   Column('product_type', String(128)),
   Column('name', String(128)),
   Column('mark', String(128)),
   Column('material', String(128), default=''),
   Column('sortament', String(128), default=''),
   Column('weight', String(128), default=''),
   )


specification_table = Table('specification', metadata,
    Column('spec_line_id', Integer, primary_key=True),
    Column('master_id', Integer, ForeignKey("products.product_id"),
        nullable=True),
    Column('slave_id', Integer, ForeignKey("products.product_id"),
        nullable=True),
    Column('quantity', Float, default=1.),
    )


class Product(object):

    def __init__(self, name, mark=''):
        self.name = name
        self.mark = mark

    def __repr__(self):
        return '<%s %s>' % (self.__class__.__name__, self.name)


class Detail(Product):

    def __init__(self, name, mark='', material='', sortament='', weight=''):
        self.name = name
        self.mark = mark
        self.material = material
        self.sortament = sortament
        self.weight = weight


class Assembly(Product): pass


class SpecLine(object):
    
    def __init__(self, master=None, slave=None, quantity=1):
        self.master = master
        self.slave = slave
        self.quantity = quantity
    
    def __repr__(self):
        return '<%s %.01f %s>' % (
            self.__class__.__name__,
            self.quantity or 0.,
            getattr(self.slave, 'name', None)
            )



product_mapper = mapper(Product, products_table,
    polymorphic_on=products_table.c.product_type,
    polymorphic_identity='product')

detail_mapper = mapper(Detail, inherits=product_mapper,
    polymorphic_identity='detail')

assembly_mapper = mapper(Assembly, inherits=product_mapper,
    polymorphic_identity='assembly')

specification_mapper = mapper(SpecLine, specification_table,
    properties=dict(
        master=relation(Assembly,
            foreignkey=specification_table.c.master_id,
            primaryjoin=specification_table.c.master_id==products_table.c.product_id,
            lazy=True, backref='specification', uselist=False),
        slave=relation(Product, 
            foreignkey=specification_table.c.slave_id,
            primaryjoin=specification_table.c.slave_id==products_table.c.product_id,
            lazy=True, uselist=False),
        quantity=specification_table.c.quantity,
        )
    )

assembly_mapper.add_property('specification',
    relation(SpecLine,
        primaryjoin=specification_table.c.master_id==products_table.c.product_id,
        lazy=True, private=True, backref='master')
    )




metadata.create_all()
session = create_session()


a1 = Assembly(name='a1')

p1 = Product(name='p1')
a1.specification.append(SpecLine(slave=p1))

d1 = Detail(name='d1')
a1.specification.append(SpecLine(slave=d1))

session.save(a1)

session.flush()
session.clear()

a1 = session.query(Product).get_by(name='a1')
print a1
print a1.specification