its a bug, and theres a new ticket http://www.sqlalchemy.org/trac/ticket/1997
with a small patch.
I would suggest maybe not using composites for this for now. Most of what
composite does you can accomplish using descriptors:
class Value(object):
@property
def custom_values(self):
return CustomValue(self.v1, self.v2)
@custom_values.setter
def custom_values(self, value):
self.v1 = value.v1
self.v2 = value.v2
I considered replacing the mechanism of composite with the above type of thing
in 0.7 but there were still some edge cases that composites seem to have.
On Dec 7, 2010, at 1:54 PM, Will wrote:
> from sqlalchemy import create_engine
> from sqlalchemy.orm import sessionmaker, mapper, relationship,
> composite
> from sqlalchemy.schema import Table, Column, MetaData, ForeignKey
> from sqlalchemy.sql import select
> from sqlalchemy.types import Integer, Text
>
> engine = create_engine('sqlite:///')
> session = sessionmaker(bind=engine, autocommit=True)()
> metadata = MetaData(engine)
>
>
> # Tables
> descriptions_table = Table('descriptions', metadata,
> Column('id', Integer, primary_key=True),
> Column('d1', Text),
> Column('d2', Text),
> )
>
> values_table = Table('values', metadata,
> Column('id', Integer, primary_key=True),
> Column('description_id', Integer, ForeignKey('descriptions.id'),
> nullable=False),
> Column('v1', Text),
> Column('v2', Text),
> )
>
> desc_values = select(
> [values_table, descriptions_table.c.d1, descriptions_table.c.d2],
> descriptions_table.c.id == values_table.c.description_id
> ).alias('descriptions_values')
>
>
> # Classes
> class Descriptions(object):
> pass
>
>
> class Values(object):
> pass
>
>
> class CustomValues(list):
>
> def __init__(self, *args):
> self.extend(args)
>
> def __composite_values__(self):
> return self
>
>
> # Mappers
> mapper(Descriptions, descriptions_table, properties={
> 'values': relationship(Values, lazy='dynamic'),
> 'custom_descriptions': composite(CustomValues,
> descriptions_table.c.d1,
> descriptions_table.c.d2),
> })
>
> mapper(Values, desc_values, properties={
> 'custom_descriptions': composite(CustomValues, desc_values.c.v1,
> desc_values.c.v2),
> })
>
>
> # Testing
> metadata.create_all()
> engine.echo = True
>
>
> descriptions = Descriptions()
> descriptions.custom_descriptions = CustomValues('Color', 'Number')
>
> values1 = Values()
> values1.custom_values = CustomValues('Red', '5')
>
> values2 = Values()
> values2.custom_values = CustomValues('Blue', '1')
>
> descriptions.values.append(values1)
> descriptions.values.append(values2)
>
> session.add(descriptions)
> session.flush()
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