Hi, all!
I want to see metaclasses in cython. So I look into the code and I see
that classes are generated like this:
class Foo:
xxx = 111
is transformed in something like:
Foo = Pyx_CreateClass('Foo', bases=(), attrs={})
# and then it does setattr()
Foo.xxx = 111
So nothing to do with metaclasses in Pyx_CreateClass() as attributes
are set after class is actually created ;(
Btw if class dict will be filled before class creation it's easy to
handle metaclass stuff in Pyx_CreateClass.
This this should be hard as PyDict_SetItem() and PyDict_GetItem()
should be used while class body creation
In python it works like this:
# based on Python/ceval.c:build_class()
def create_class(name, bases, attrs):
if '__metaclass__' in attrs:
metaclass = attrs.get('__metaclass__')
elif len(bases) > 0:
base = bases[0]
if hasattr(base, '__class__'):
metaclass = base.__class__
else:
metaclass = type(base)
else '__metaclass__' in globals():
metaclass = globals().get('__metaclass__')
else:
metaclass = type
return metaclass(name, bases, attrs)
Another tricky way is to transform ClassDefNode, that has
__metaclass__ attribute into two classes:
class Foo(object):
__metaclass__ = Bar
xxx = 111
transform into:
Foo = create_class('Foo', (), {})
Foo.xxx = 111
Foo = create_class('Foo', (object,), Foo.__dict__())
Second way is much easy to implement (I think) adding
MetaclassTransform into pipeline, but seems to be dirty hack.
I want to ask what is the best way to implement this?
vitja.
_______________________________________________
Cython-dev mailing list
[email protected]
http://codespeak.net/mailman/listinfo/cython-dev
