[Zope3-dev] Schema, widget and form refactoring (was Re: [Zope3-checkins]CVS:Zope3/src/zope/schema - _bootstrapfields.py:1.19.2.1)

[Garrett Smith]

andre wrote:
> I'm a new comer to Zope3, i suppose missing_value might have a very
> special meaning in some implementation.
> English is not my mother language but it seems to me that :
>=20
> None is nothing in every case,

I agree, and would tend to implement my software this way. But, as Steve
Alexander argued, and I think correctly so, we need to support existing
code without requiring the author to change it.

And here's an example that might trip you up:

  <field type=3D"string" value=3D"" />

How do you get None out of this data structure to use as your missing
value?

  <field type=3D"string" value=3D"None" />  <!-- doh! -->

Fact is, unless you changed the DTD to support something like this:

  <field type=3D"string" missing=3D"True" />

there'd be no way to use None as the missing value.

Btw, the folks who expect None as their missing value will be happy 100%
of the time -- it's the default.

 -- Garrett