Viewlets
A viewlet’s render() method needs to return unicode objects because the
standard zope3 viewlet implementation concatenates the output of various
viewlet render()’s. If the output is a str, then implicit
conversion-to-unicode will happen using the default python character encoding
which is most often ascii (causing a utf-8 encoded str with non-ascii chars
to blow up).
Archetypes Schema Fields
Archetypes (as present in Plone 2.5 and 3.0, and possibly older) stores all
StringField fields as utf-8 encoded str’s irrelevant of what the Plone site
encoding has been configured as. Safest way to handle this is to always
feed StringField field mutators unicode objects instead of str’s. And upon
retrieval, be prepared to decode the str’s using utf-8
(ie context.Title().decode(’utf-8′) => u’someval’). Remember, StringField
accessors will always return utf-8 encoded str’s and Zope 3 often makes
assumptions that the string values it’s dealing with are unicode objects.
Summing Up
Use unicode objects everywhere. If some Zope 2 / Plone API
forces you to use str’s or get str’s convert them to
unicode’s before doing anything else.
Rocky Burt: Zope 3 in Zope 2 Gotcha’s: Unicode
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