[storm] Fwd: question about valitation

[Sean Upton]

Oops - forgot to reply-to-list... see below.


On Fri, Mar 28, 2008 at 10:15 AM, Massimo <max at studiomasson.it> wrote:
 > Hi everybody,
 >  I have another newbie question, please beg my pardon...
 >
 >  I'm wondering how to implement a "validation" function for a storm
 >  class/object.

 I think you could subclass an existing property type (e.g. Int,
 Unicode), or possibly storm.property.Property (requires a bit more
 work).  Your property class would implement __set__(), which might
 look like (untested):

 from storm.variable import IntVariable

 class MyValidatingInt(Property):
    def __init__(self, name, primary=False,
 variable_class=IntVariable, **kwargs):
        self._name = name
        kwargs["value"] = kwargs.pop("default", Undef)
        kwargs["value_factory"] = kwargs.pop("default_factory", Undef)
        self._variable_kwargs = kwargs
        self._variable_class = variable_class
        self._primary = primary

    def validate(self, obj, value):
        if type(value) is not int or value < 42:
            raise ValidationError, 'bad data'
        if value > obj.maxfoo:
            raise ValidationError, 'constraint is not met'
    def __set__(self, obj, value):
        if obj is not None:
            self.validate(obj, value)
        Property.__set__(self, obj, value)


 On another note, have you looked at using zope.interface/zope.schema?
 In addition to simple field validation, you can do multi-field
 "invariant" validation using zope.schema, and it is not that difficult
 to map many zope schema fields to storm properties in a way similar to
 what I've documented above (I have similar code doing just that, using
 zope.schema field validation).

 Sean