On Jul 13, 2010, at 10:21 AM, sacabuche wrote:
> I was trying to get the last value "before_insert" a new item but i
> didn't find out, so i change of strategy and i saved the last value of
> this method, but the problem is that when i do other commits my old
> MapperExtension attribute (self.last_value) get the last value and i
> dislike it, even when I close and open a new Session (discovered in my
> tests)
>
> This is my code:
>
> class _ValueExtension(MapperExtension):
> """Set new value for SkuDynamic and SKuUnique"""
> def __init__(self):
> self.last_value = {} # <<--- THE PROBLEM
> self.first_value = FIRST_VALUE
>
>
> def before_insert(self, mapper, connection, instance):
> session = object_session(instance)
> cls = instance.__class__
>
> last_sku_value = self.get_last_value(session, cls, instance)
>
>
> if not last_sku_value:
> instance.value = self.first_value
> else:
> instance.value = next_value(last_sku_value)
>
> self.last_value[self.last_value_key] = instance.value
> self.set_values(instance)
>
> #def after_insert(self, mapper, connection, instance):
> # self.__init__() #<--- IF I DO THIS I DON'T HAVE THE LAST
> VALUE IN THE SAME FLUSH
>
> #def after_update(self, mapper, connection, instance):
> # self.__init__()
>
>
> def get_last_value(self, session, cls, instance):
> """This have to return just one value
> and set self.last_value_key is nedded to update elements in same
> session
> Execute The Query or check self.last_value
> """
> raise NotImplementedError, 'implement this function'
>
> def set_values(self, instance):
> """Use if necesary"""
> pass
A MapperExtension is persistent for the life of the application and also is
accessed concurrently, so it is not an appropriate place to store a count for
things things that are local to a specific flush, and its really not a good
place in general to do what you're trying to do (though its not clear above
what you're trying to accomplish, if you want a global "last sku" or a "sku"
specific to one flush).
You'd be better off querying the database for the "last sku value" when you
need it, or just adding code to your classes __init__() method to keep track of
sku numbers in memory as needed.
>
>
> Thanks
>
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