> i sat on this problem for 10 hours now and i have no idea anymore. if anyone could give me  a hint, i would really appreciate that.

> story: i created a schema for a custom widget, wich renders, the form works, all fine so far.

> problem: i need to create a nested schema so i can access ``children`` in my custom widget to transmit more than only one filed. i had different variations of schemas so far, which all kinda work - e.g. render - but on validation my problem is i cannot access the POST data of the children in my parent-schema.
> now i just wanted to see if i can access them at least in a custom validator (http://deformdemo.repoze.org/interfield/), nope. also the preparer just doesn't work on the parent-schema.

> here is all relevant code, maybe someone spots an error.

> thanks, andi

> class curry(object):
>     """
>     class to curry a methods together with fewer arguments.

>     @see: http://code.activestate.com/recipes/52549-curry-associating-parameter...
>     """
>     def __init__(self, fun, *args, **kwargs):
>         self.fun = fun
>         self.pending = args[:]
>         self.kwargs = kwargs.copy()

>     def __call__(self, *args, **kwargs):
>         if kwargs and self.kwargs:
>             kw = self.kwargs.copy()
>             kw.update(kwargs)
>         else:
>             kw = kwargs or self.kwargs

>         return self.fun(*(self.pending + args), **kw)

> @colander.deferred
> def create_LocationPickerWidget(node, kw):
>     """
>     callable to create the widget with a deferred paramater, here
>     "request"

>     gets applied by ``colander.Schema.bind(request=self.request)``
>     """
>     request = kw["request"]
>     return LocationPickerWidget(request)

> class Location(colander.MappingSchema):
>     location_search = colander.SchemaNode(
>         colander.String(),
>         name = "location_string.location_search",
>         validator=colander.Length(min=1),
>     )
>     location_point = colander.SchemaNode(
>         colander.String(),
>         name = "location_string.location_point",
>         widget = deform.widget.HiddenWidget(),
>         validator=colander.Length(min=1),
>     )

> class LocationPicker(colander.MappingSchema):
>     """
>     schema only for a step in the form to choose a location

>     @see http://docs.pylonsproject.org/projects/colander/en/latest/manipulatio...
>     """
>     location_string = Location(
>         widget=create_LocationPickerWidget,
>     )

>     @classmethod
>     def prepare_location(cls, fieldname, value):
>         """
>         deform preparer to convert a form submitted location in a real
>         location.

>         appended below
>         """
>         if log.isEnabledFor(logging.WARN):
>             _out = StringIO()
>             pprint(value, stream=_out)
>             log.warn("%s.%s @%s value: %s", __name__, cls.__name__, fieldname, _out.getvalue())

>         if value:
>             lat, lng = value.split(',')
>             position = WKTSpatialElement('POINT({0} {1})'.format(lat, lng))
>             return position
>         return value

> # adding a preparer to the mapping node will not work
> LocationPicker.location_string.preparer =\
>         curry(LocationPicker.prepare_location, "XX_location_string_XX")
> # those work
> Location.location_search.preparer =\
>         curry(LocationPicker.prepare_location, "location_search")
> Location.location_point.preparer =\
>         curry(LocationPicker.prepare_location, "location_point")