[Zope3-Users] Should I be using a more basic form in Formlib than EditForm?

[Adam Summers]

Hi all,  

I have an edit form:
class claimEditForm(form.EditForm):
    form_fields = form.Fields(Iclaim).omit('__name__', '__parent__')

    @form.action(_("MyApply"), condition=form.haveInputWidgets)   
    def handle_edit_action(self, action, data):
        if self.context.modify(data):
            self.status = _(u"Object Updated")
        else:
            self.status = _(u"No Changes")

The object has a modify method, which looks like this:
    def modify(self, kw):
        fieldnames = getFieldNames(Iclaim)
        for k in kw.keys():
            if k not in fieldnames:
                raise Invalid("Invalid Field to set: %s", k)
            else:
                field = Iclaim[k]
                field.validate(kw[k])
                setattr(self, k, kw[k])
        self._completeValues() ###This method calculates some missing 
data for the object (if possible) or raises an error
        Iclaim.validateInvariants(self)
        return True

The thing I don't understand is this: The invariant method I have in the 
interface is being called twice.

First Pass through, object passed to my invariant is of type:
    FormData: <zope.formlib.form.FormData instance at 0x3f07c10>

Call stack is:
    debug_call [publish.py:114]   
    __call__ [form.py:773]   
    update [form.py:740]   
    handleSubmit [form.py:683]   
    validate [form.py:720]   
    checkInvariants [form.py:504]   
    validateInvariants [interface.py:583]   
    claimInvariants [interfaces.py:39]

(In certain cases the data will be invalid, because I need to prep a few 
fields via claim._completeValues() )

Second Pass through, object passed to my invariant function is of type:
    claim: <as.claim.claim.claim object at 0x3591770>

Call stack is:
    debug_call [publish.py:114]    
    __call__ [form.py:773]    
    update [form.py:754]    
    success [form.py:598]    
    handle_edit_action [forms.py:23] (This is my action being called 
now!)    
    modify [claim.py:42] (At this point in the code, the 
as.claim.claim.claim object has been modified with the contents of the 
form)    
    validateInvariants [interface.py:583]    
    claimInvariants [interfaces.py:39]    
  

My question is: In order to not have the variants checked before my data 
is prepped, should I really be using a form.EditForm as the base, or 
some other class?

Many thanks in advance, and a happy new year
Adam