[Zope-dev] z3c.form - creating a file upload widget

[Martin Aspeli]

Hi,

I'm writing a custom file widget for z3c.form that works like the 
Archetypes file widget that Plone uses and the formlib widget in 
collective.namedfile. That is, after you've uploaded a file once, you're 
given a radio button to decide whether to upload a new file, or leave 
the existing file in place.

I can't quite figure out how to do this, though. I've tried to override 
the extract() method on the widget to look in the request for the 
special marker that says "user chose not to change the file". However, I 
don't know what to return. If I return NOVALUE, then validation fails 
(if the field is required). If I try to look up the field value from the 
data manager and return it, it ends up setting the field back on itself, 
which is wasteful.

Any clues?

Cheers,
Martin

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