I have the following setup (attached python file).
I'm using an inheritance hierarchy without a discriminator field, deriving
from AbstractBase.
I want to be able to use the "keywords" attribute in the "SuperUser" class,
and from the documentation I understand I need to redefine it, however that
doesn't seem to work.
I assume I could manually use a primary join there (as the error
indicates), but as I understand that's exactly what "AbstractBase" class
should handle...
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from sqlalchemy import ForeignKey
from sqlalchemy import Integer
from sqlalchemy import Column
from sqlalchemy import String
from sqlalchemy import create_engine
from sqlalchemy.ext.associationproxy import association_proxy
from sqlalchemy.ext.declarative import ConcreteBase
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relationship, backref
from sqlalchemy.orm import sessionmaker
Base = declarative_base()
# Inheritance without discriminator
class User(ConcreteBase, Base):
__tablename__ = 'user'
id = Column(Integer, primary_key=True)
keywords = association_proxy('user_keywords', 'keyword')
__mapper_args__ = {'polymorphic_identity': 'user', 'concrete': True}
class UserKeyword(Base):
__tablename__ = 'user_keyword'
user_id = Column(Integer, ForeignKey('user.id'), primary_key=True)
keyword_id = Column(Integer, ForeignKey('keyword.id'), primary_key=True)
special_key = Column(String(50))
user = relationship(User,
backref=backref("user_keywords",
cascade="all, delete-orphan")
)
keyword = relationship("Keyword")
def __init__(self, keyword=None, user=None, special_key=None):
self.user = user
self.keyword = keyword
self.special_key = special_key
class Keyword(Base):
__tablename__ = 'keyword'
id = Column(Integer, primary_key=True)
keyword = Column('keyword', String(64))
def __init__(self, keyword):
self.keyword = keyword
def __repr__(self):
return 'Keyword(%s)' % repr(self.keyword)
class SuperUser(User):
__tablename__ = 'super_user'
id = Column(Integer, ForeignKey(User.id), primary_key=True)
role = Column(String(64))
__mapper_args__ = {'polymorphic_identity': 'super_user', 'concrete': True}
# ????
user_keywords = relationship(UserKeyword)
keywords = association_proxy('user_keywords', 'keyword')
engine = create_engine('sqlite:///:memory:', echo=False)
Base.metadata.create_all(engine)
Session = sessionmaker(bind=engine)
session = Session()
user = SuperUser()
for kw in (Keyword('new_from_blammo'), Keyword('its_big')):
user.keywords.append(kw)
session.add(user)
session.commit()
