Hi,
I have a similar task, so I tried to use your proposal, but it didn't
work for me:
===
from sqlalchemy import types as satypes
from sqlalchemy import schema as saschema
from sqlalchemy.engine import create_engine
from sqlalchemy.ext.declarative import declarative_base,
DeclarativeMeta
from sqlalchemy.orm import scoped_session, sessionmaker
class BaseType(DeclarativeMeta):
def __init__(newcls, classname, bases, dict_):
newcls.notes = saschema.Column(satypes.String)
DeclarativeMeta.__init__(newcls, classname, bases, dict_)
MetaData = saschema.MetaData(bind=create_engine('sqlite:///:memory:'))
Session = scoped_session(sessionmaker(bind=MetaData.bind))
Base = declarative_base(metadata=MetaData, mapper=Session.mapper,
metaclass=BaseType)
class MasterEntity(Base):
__tablename__ = "master"
id = saschema.Column(satypes.Integer, primary_key=True)
status = saschema.Column(satypes.CHAR(length=1), default="A")
print [ _c.key for _c in MasterEntity.__table__.columns ]
# ['id', 'status']
# => the 'notes' column is missing
=== snip
So, what am I doing wrong?
Thanks in advance,
Frank
Btw.: Hello group and many thanks to Michael for this great piece of
software!
On Dec 16, 6:58 pm, Michael Bayer <mike...@zzzcomputing.com> wrote:
> anabstractbaseclassisn't going to set up the same fields on all
> descendants since the mapper()/Table() setup occurs during the
> creation of the individualclassusing the non-inheritedclassdict,
> and unique instances of each of the Column, etc. elements are required
> as well.
>
> "concrete inheritance", as referenced in that post, was not designed
> to be used as a configurational spacesaver and always requires a
> mapped selectable for the "base", which you don't have here, so it's
> not appropriate for this use case.
>
> So for this you'd need a custom metaclass:
>
> classMyMeta(DeclarativeMeta):
> def __init__(cls, classname, bases, dict_):
> cls.notes = Column(String)
> DeclarativeMeta.__init__(cls, classname, bases, dict_)
>
> Base= declarative_base(metaclass=MyMeta)
>
> On Dec 16, 2008, at 12:36 PM, Joril wrote:
>
>
>
> > Hi everyone!
> > I need to declare a few unrelated classes (from a "business"
> > perspective) that share some attributes/fields, so I thought I could
> > use anabstractclassto group these common attributes (note that just
> > a few classes should have them, not every one)
>
> > This post
> >http://groups.google.it/group/sqlalchemy/msg/d3de02f609a0bbd9?hl=it
> > suggests to use mixins, but I can't get it to work, SQLA generates the
> > tables without the common fields.
>
> > I'm testing it with this script:
>
> >> from sqlalchemy.ext.declarative import declarative_base
> >> from sqlalchemy import Column, Integer, String
> >> from sqlalchemy import create_engine
>
> >> # --- Tables definition
> >>Base= declarative_base()
>
> >>classAbstract(object):
> >> notes = Column(String)
>
> >>classConcrete(Base,Abstract):
> >> __tablename__ = 'concrete'
> >> id = Column(Integer, primary_key=True)
> >> # ---
>
> >> # DB creation
> >> engine = create_engine('sqlite:///:memory:', echo=True)
> >>Base.metadata.create_all(engine)
>
> > Here's the sql call:
> >> CREATE TABLE concrete (
> >> id INTEGER NOT NULL,
> >> PRIMARY KEY (id)
> >> )
>
> > What am I missing? Did I misunderstood how the mixin should be used?
> > (I'm using SQLA 0.5rc4)
>
> > Many thanks!
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