On Sep 18, 2008, at 6:59 AM, GHZ wrote:
>
> I want to set table, mapper arguments automatically.
> The following is the only way I have found to do this.
> Is this supported?
> Am I wasting my time with Declarative and should rather use the non
> declarative if I want this control?
>
> class MyMeta(DeclarativeMeta):
>
> def __new__(meta, classname, bases, classdict):
>
> # Copy interesting arguments from base classes
> for base in bases:
> for arg in (a for a in ('__table_args__',
> '__tablename__',
> '__mapper_args__') if a in
> base.__dict__):
> classdict[arg] = base.__dict__[arg]
>
> return DeclarativeMeta.__new__(meta, classname, bases,
> classdict)
>
> Base = declarative_base(bind=engine)
>
> class MyDeclarativeStuff(object):
> # Set some generic stuff up.
> __table_args__ = {'autoload':True}
>
> class Customer(Base, MyDeclarativeStuff):
> __metaclass__ = MyMeta
> __tablename__ = 'customer'
Well, I would think "__table_args__" is the only argument you'd really
want to propigate in that way, and this is an inconvenience I've also
had so perhaps we'll do something about it...I would propose a
"default_table_args" keyword arg to declarative_base().
As for mapper args, I'd just supply a mapper callable to
declarative_base() which sets up the desired **kwargs (like
extensions), and returns a mapper() from that (its an available kwarg).
Check out the **kwargs for declarative_base, as it also takes a
"metaclass" argument so you wouldn't need to jump through the hoops
you're jumping. Also, the individual components within
declarative_base() are availalble as separate functions, so you could
build a recipe like the above more directly. Check out the source.
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