[Zope] Trapping empty form values ...

[Darran Edmundson]

Someone recently posted asking how to trap empty form values
in ZClass constructors.  I stumbled across Zen's How-To
"http://www.zope.org/Members/Zen/howto/FormVariableTypes"
which contains the answer:

    "When the [name] form field is left blank, :ignore_empty 
     skips over the variable rather than returning a null 
     string as its value."

Note, it seems that it's necessary to also indicate the field 
type, ie., use varname:string:ignore_empty rather than 
just varname:ignore_empty which will not work.

Cheers,
Darran.