I think I understand what you trying to do
in fact polymorphic objects are load correctly in my test, I think it is
an approach to your case.
follow the code I used before to ask about polymorphic inheritance, note
to the Catalog class, this class have a resource list (catalog_id on
Resource), and I am inserting different types of resources, than when
select,
each resource is loaded correctly with their type
---code------8<------code-----
from sqlalchemy import create_engine, MetaData, Table, Column, types,
ForeignKey
from sqlalchemy.orm import mapper, relation, backref, create_session
from sqlalchemy.sql.expression import outerjoin, join
from sqlalchemy import String, Unicode, Integer, DateTime, Numeric,
Boolean, UnicodeText
db = create_engine('sqlite:///:memory:')
metadata = MetaData()
metadata = MetaData(db)
metadata.bind = db
session = create_session(bind=db)
resource_table = Table('resource', metadata,
Column('id',Integer, primary_key=True),
Column('name', String(30)),
Column('catalog_id', Integer, ForeignKey('catalog.id')),
Column('poly', String(31), nullable=True)
)
person_table = Table('person', metadata,
Column('id',Integer, ForeignKey('resource.id'), primary_key=True,),
)
material_table = Table('material', metadata,
Column('id',Integer, ForeignKey('resource.id'), primary_key=True,),
)
employee_table = Table('employee', metadata,
Column('id',Integer, ForeignKey('person.id'), primary_key=True),
)
technical_table = Table('technical', metadata,
Column('id',Integer, ForeignKey('person.id'), primary_key=True),
)
catalog_table = Table('catalog', metadata,
Column('id',Integer, primary_key=True),
)
catalog_resources = Table('catalog_resources', metadata,
Column('id', Integer, primary_key=True),
Column('resource_id',Integer, ForeignKey('resource.id')),
)
class Resource(object):
def __init__(self, name):
self.name = name
def __repr__(self):
return "Resource < id=%d ,name=%s >" % (self.id,self.name)
class Person(Resource):
def __repr__(self):
return "Person < id=%d ,name=%s >" % (self.id,self.name)
class Material(Resource):
def __repr__(self):
return "Material < id=%d ,name=%s >" % (self.id,self.name)
class Employee(Person):
def __repr__(self):
return "Employee < id=%d ,name=%s >" % (self.id,self.name)
class Technical(Person):
def __repr__(self):
return "Technical < id=%d ,name=%s >" % (self.id,self.name)
class Catalog(object):
def __repr__(self):
return "catalog < id=%d resources=%s >" %
(self.id,str([str(r)+',' for r in self.resources]))
mapper(Resource, resource_table,
polymorphic_on=resource_table.c.poly,
polymorphic_identity='resource',
)
mapper(Person, person_table,
inherits=Resource, polymorphic_identity='person',
polymorphic_on= resource_table.c.poly,
)
mapper(Material, material_table,
inherit_condition= material_table.c.id == resource_table.c.id,
inherits=Resource, polymorphic_identity='material'
)
mapper(Employee, employee_table,
inherit_condition= employee_table.c.id == person_table.c.id,
inherits=Person, polymorphic_identity='employee',
)
mapper(Technical, technical_table,
inherit_condition= technical_table.c.id == person_table.c.id,
inherits=Person, polymorphic_identity='technical',
)
mapper(Catalog, catalog_table,
properties={
'resources':relation(Resource)
})
metadata.create_all(bind=db)
r = Resource('resource name')
p = Person('person name')
m = Material('material name')
e = Employee('employee name')
t = Technical('technical name')
x = Catalog()
x.resources = [p,m,e,t]
session.save(r)
session.save(p)
session.save(m)
session.save(e)
session.save(t)
session.save(x)
session.flush()
session.clear()
print "############ LIST FROM RESOURCES #################"
for o in session.query(Resource).all():
print o, o.poly
print "############ LIST FROM PERSONS #################"
for o in session.query(Person).all():
print o, o.poly
print "############ Catalog #################"
y= session.query(Catalog).one()
print y
---code------8<------code-----
I Hope it helps you
Att
--
Alexandre da Silva
Analista de Sistemas - Bacharel em Sistemas de Informação (2003-2007)
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