ForEach and NestedVariables in FormEncode to create array of form items in Pyramid

I'm using Pyramid with FormEncode to try and create and validate a list of addresses. I'm using pyramid_simpleform and have been looking at this tutorial http://jimmyg.org/blog/2007/multiple-checkboxes-with-formencode.html and this previous question Pylons FormEncode with an array of form elements but I'm still having some issues. My structure is currently as follows:

Schema:

from formencode import Schema, validators, ForEach, NestedVariables

class AddressSchema(Schema):
allow_extra_fields = False
addresses = validators.String(not_empty=True)

class JobSchema(Schema):
filter_extra_fields = True
allow_extra_fields = True
pre_validators = [NestedVariables()]
job_name = validators.MinLength(5, not_empty=True)
comments = validators.MinLength(5, not_empty=False)
addresses = ForEach(AddressSchema())

Template:

${renderer.errorlist("addresses")}
${renderer.errorlist("job_name")}

<p><label for="job_name">Job name: </label>${renderer.text("job_name", size=30)}</p>
% for a in range(1, initial_number_of_address_fields):
    <p><label for="addresses-${a}">Address: </label>${renderer.textarea("addresses-" + str(a), cols=39, rows=6)}</p>
% endfor
${renderer.submit("submit", "Submit")}

View:

@view_config(route_name='add_addresses', renderer="add_addresses.mak")
def add_addresses(request):

from myproject.forms import JobSchema
from myproject.models import Job
from formencode import htmlfill, variabledecode, ForEach

initial_number_of_address_fields = 5

form = Form(request, schema=JobSchema(), variable_decode=False)
renderer = FormRenderer(form)

# if the form has been submitted
if 'submit' in request.POST:

    if form.validate(): # uses validation specified in forms.py

        # automatically bind to provided form
        obj = form.bind(Job()) # no exisiting id provided, so a new document is created
        # add some additional values
        obj.__setattr__("last_updated_on", datetime.date.today().strftime('%Y/%m/%d'))
        #save
        obj.save()
        return HTTPFound(location="/")

return {
    'title':'Add addresses',
    'initial_number_of_address_fields': initial_number_of_address_fields, 
    'renderer': renderer
}

I get back actual validation errors like so:

{'addresses': u'Missing value'}

But properly filled out values also provide an error:

The input must be dict-like (not a : u'dgfgfd')

If I change variable_decode to True (in the form variab开发者_JAVA百科le setup) I no longer get any errors back at all. I think I'm supposed to be using variable_decode somehow, but I'm not sure how. How do I properly validate these values?

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I have written a blog post with similar usage back in 2009, it may come in handy:

http://www.domenkozar.com/2009/07/22/advanced-formencode-usage/