Setting field value from AutoExtensibleForm

If I have a AutoExtensibleForm with
ignoreContext = True

Is it still possible to set the value of a field (from button handler ) ?
Something like this

class DoSomeStuffForm(AutoExtensibleForm, form.Form):
    """ Looks at the fields and copies some stuff and creates content types
         acording to what was chosen / selected

    schema = ImyForm
    ignoreContext = True

    @button.buttonAndHandler(u'Do your stuff')
    def handleApply(self, action):
       #Do a lot of stuff here
       #change hidden field so we can index 'finished /executed '
       self.context.isCompleted = True

It should; what happens if you try it?

the field is (still) 'False' the next time I 'visit'.

What is self.context ?

it is context

If the field is visible it seems to work. Not sure why that should matter, I will just hide it with CSS for now.