[Zope-dev] z3c.form: TextLineConverter and IFromUnicode

[Martin Aspeli]

Hi,

Sorry for doing this by email rather than unit test, but I'm a bit 
over-stretched at the moment.

plone.z3cform has a backport of z3c.form trunk's TextLines widget 
(when's that release coming, any ideas?).

In using it, I discovered that the converter (converter.py on z3c.form 
trunk) does this:

     def toFieldValue(self, value):
         """See interfaces.IDataConverter"""
         widget = self.widget
         collectionType = self.field._type
         if isinstance(collectionType, tuple):
             collectionType = collectionType[-1]
         if not len(value):
             return self.field.missing_value
         valueType = self.field.value_type._type
         if isinstance(valueType, tuple):
             valueType = valueType[0]
         return collectionType(valueType(v) for v in value.split())

I was just wondering: should we not try to use IFromUnicode when 
converting the value type? This would be safer, and probably allow us to 
support more value_types. Arguably, we should *require* that the 
value_type for this widget provides IFromUnicode, but we could have the 
fallback _type cast like this.

A simple implementation would be:

     def toFieldValue(self, value):
         """See interfaces.IDataConverter"""
         widget = self.widget
         collectionType = self.field._type
         if isinstance(collectionType, tuple):
             collectionType = collectionType[-1]
         if not len(value):
             return self.field.missing_value

         value_type = self.field.value_type
         cast = None
         fromUnicode = IFromUnicode(value_type, None)
         if fromUnicode is not None:
             cast = fromUnicode.fromUnicode
         else:
             cast = value_type._type
             if isinstance(cast, (tuple,list)):
                 cast = cast[0]
         return collectionType(cast(v) for v in value.split())

Martin

-- 
Author of `Professional Plone Development`, a book for developers who
want to work with Plone. See http://martinaspeli.net/plone-book