meta.py

import inspect
import logging


class MetaObject(object):

    class Implementation(object):

        def __init__(self, meta):
            assert isinstance(meta, MetaObject), type(meta)
            self._meta = meta

        @property
        def meta(self):
            return self._meta

        def __str__(self):
            return "<%s.%s>" % (self._meta.__class__.__name__, self.__class__.__name__)

    def __init__(self):
        super(MetaObject, self).__init__()
        self._logger = logging.getLogger(self.__class__.__name__)

    def __str__(self):
        return "<%s>" % self.__class__.__name__

    def implement_class(self, cls, *args, **kargs):
        assert cls == self.Implementation or cls in self.Implementation.__subclasses__(), (cls, self.Implementation)
        if __debug__:
            try:
                return cls(self, *args, **kargs)
            except TypeError:
                self._logger.error("TypeError in %s.%s", self.__class__.__name__, self.Implementation.__name__)
                self._logger.error("self.Implementation takes: %s", inspect.getargspec(self.Implementation.__init__))
                self._logger.error("self.Implementation got: %s %s", args, kargs)
                raise

        else:
            return cls(self, *args, **kargs)

    def implement(self, *args, **kargs):
        if __debug__:
            return self.implement_class(self.Implementation, *args, **kargs)

        else:
            return self.Implementation(self, *args, **kargs)