Your form would have to be constructed based on some variables passed to it from your POST (or blindly check for attributes). The form itself is constructed every time the view is reloaded, errors or not, so the HTML needs to contain information about how many fields there are to construct the correct amount of fields for validation.
I’d look at this problem the way FormSet
s work: there is a hidden field that contains the number of forms active, and each form name is prepended with the form index.
In fact, you could make a one field FormSet
https://docs.djangoproject.com/en/dev/topics/forms/formsets/#formsets
If you don’t want to use a FormSet
you can always create this behavior yourself.
Here’s one made from scratch – it should give you some ideas. It also answers your questions about passing arguments to __init__
– you just pass arguments to an objects constructor: MyForm('arg1', 'arg2', kwarg1='keyword arg')
Forms
class MyForm(forms.Form):
original_field = forms.CharField()
extra_field_count = forms.CharField(widget=forms.HiddenInput())
def __init__(self, *args, **kwargs):
extra_fields = kwargs.pop('extra', 0)
super(MyForm, self).__init__(*args, **kwargs)
self.fields['extra_field_count'].initial = extra_fields
for index in range(int(extra_fields)):
# generate extra fields in the number specified via extra_fields
self.fields['extra_field_{index}'.format(index=index)] = \
forms.CharField()
View
def myview(request):
if request.method == 'POST':
form = MyForm(request.POST, extra=request.POST.get('extra_field_count'))
if form.is_valid():
print "valid!"
else:
form = MyForm()
return render(request, "template", { 'form': form })
HTML
<form>
<div id="forms">
{{ form.as_p }}
</div>
<button id="add-another">add another</button>
<input type="submit" />
</form>
JS
<script>
let form_count = Number($("[name=extra_field_count]").val());
// get extra form count so we know what index to use for the next item.
$("#add-another").click(function() {
form_count ++;
let element = $('<input type="text"/>');
element.attr('name', 'extra_field_' + form_count);
$("#forms").append(element);
// build element and append it to our forms container
$("[name=extra_field_count]").val(form_count);
// increment form count so our view knows to populate
// that many fields for validation
})
</script>