dirty.py

# -*- coding: utf-8 -*-
from hashlib import sha1

def dirty_fabric(checkfield, *fields):
    class _dirty_field(object):
        def __init__(self):
            self._ckeckfield = checkfield
            self._fields = fields

        @property
        def _is_exist_field(self):
            k = self.__dict__.keys()
            if self._ckeckfield not in k:
                return False
            for field in self._fields:
                if field not in k:
                    return False
            return True

        @property
        def _is_valid_type(self):
            return True

        @property
        def _is_valid_field(self):
            return self._is_exist_field and self._is_valid_type

        def _get_checksum(self):
            checksum = sha1()
            for field in self._fields:
                checksum.update(self.__dict__.get(field))
            return checksum.hexdigest()

        def is_dirty(self):
            if not self._is_valid_field:
                return None
            hexdig = self._get_checksum()
            if self.__dict__.get(self._ckeckfield) == hexdig:
                return None
            return hexdig

    return _dirty_field