oops, do it like this:
class BaseType(DeclarativeMeta):
def __init__(newcls, classname, bases, dict_):
dict_['notes'] = saschema.Column(satypes.String)
DeclarativeMeta.__init__(newcls, classname, bases, dict_)
clearly we'll have to figure out a more user friendly pattern for this
use case.
On Dec 19, 2008, at 5:27 AM, FrankB wrote:
>
> 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 <[email protected]> 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!
>
> >
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"sqlalchemy" group.
To post to this group, send email to [email protected]
To unsubscribe from this group, send email to
[email protected]
For more options, visit this group at
http://groups.google.com/group/sqlalchemy?hl=en
-~----------~----~----~----~------~----~------~--~---
