On Sep 26, 2010, at 6:38 PM, Julien Iguchi-Cartigny wrote:
> Hi,
>
> I'm trying to use polymorphic_on with several inheritances:
>
> engine = create_engine(
> 'mysql://xxx:y...@localhost:3306/zzz?charset=utf8&use_unicode=0',
> pool_recycle=3600, echo=True)
>
> Base = declarative_base()
>
> class AbstractPersistent(object):
> version = Column('VERSION', Integer)
> last_modified_by = Column('LAST_MODIFIED_BY', String(255))
> last_modified_date = Column('LAST_MODIFIED_DATE', Date)
> created_by = Column('CREATED_BY', String(255))
> created_date = Column('CREATED_DATE', Date)
>
> class AbstractNamed(AbstractPersistent):
> eid = Column('ENTERPRISE_ID', String(255))
> title = Column('TITLE', String(255))
> description = Column('DESCRIPTION', String(255))
>
> class AbstractContainer(AbstractNamed):
> __tablename__ = 'CM_MEMBER_CONTAINER_T'
> id = Column('MEMBER_CONTAINER_ID',Integer,primary_key=True)
> discriminator = Column('CLASS_DISCR', String(100))
> __mapper_args__ = {'polymorphic_on': discriminator }
>
> class CourseSet(Base,AbstractContainer):
> __mapper_args__ = {'polymorphic_identity':
> 'org.sakaiproject.coursemanagement.impl.CourseSetCmImpl'}
AbstractContainer is not mapped, its a mixin, so its __mapper_args__ are not
used until a subclass of Base is invoked, which starts up a declarative
mapping. Your only mapped class then is CourseSet, which has its own
__mapper_args__ , that override those of AbstractContainer - they are ignored.
To combine __mapper_args__ from a mapped class with those of a mixin, see the
example at
http://www.sqlalchemy.org/docs/orm/extensions/declarative.html?highlight=declarative#combining-table-mapper-arguments-from-multiple-mixins
. It uses __table_args__ but the same concept of creating a full dictionary
of arguments applies for __mapper_args__ as well.
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