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# Copyright (c) 2002-2007 LOGILAB S.A. (Paris, FRANCE).
# http://www.logilab.fr/ -- mailto:contact@logilab.fr
#
# This program is free software; you can redistribute it and/or modify it under
# the terms of the GNU General Public License as published by the Free Software
# Foundation; either version 2 of the License, or (at your option) any later
# version.
#
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along with
# this program; if not, write to the Free Software Foundation, Inc.,
# 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
"""
bases class for interfaces to provide "light" interface handling.
TODO:
_ implements a check method which check that an object implements the
interface
_ Attribute objects
This module requires at least python 2.2
"""
from types import ListType, TupleType
class Interface:
"""base class for interfaces"""
def is_implemented_by(cls, instance):
return implements(instance, cls)
is_implemented_by = classmethod(is_implemented_by)
def implements(obj, interface):
"""return true if the give object (maybe an instance or class) implements
the interface
"""
kimplements = getattr(obj, '__implements__', ())
if not isinstance(kimplements, (list, tuple)):
kimplements = (kimplements,)
for implementedinterface in kimplements:
if issubclass(interface, implementedinterface):
return True
return False
def extend(klass, interface, _recurs=False):
"""add interface to klass'__implements__ if not already implemented in.
if klass is subclassed, ensure subclasses __implements__ it as well.
NOTE: klass should be e new class.
"""
if not implements(klass, interface):
try:
kimplements = klass.__implements__
kimplementsklass = type(kimplements)
kimplements = list(kimplements)
except AttributeError:
kimplementsklass = tuple
kimplements = []
kimplements.append(interface)
klass.__implements__ = kimplementsklass(kimplements)
for subklass in klass.__subclasses__():
extend(subklass, interface, _recurs=True)
elif _recurs:
for subklass in klass.__subclasses__():
extend(subklass, interface, _recurs=True)
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