django field/widget for multiple values - django

Question

I seriously can't figure out how to manage to do this.
I would like to use django forms to validate the following (unknown number of aname):
<input type="hidden" name="aname" value="someJSONdump1"/>
<input type="hidden" name="aname" value="someJSONdump2"/>
<input type="hidden" name="aname" value="someJSONdump3"/>
<input type="hidden" name="aname" value="someJSONdump4"/>
and on the django side, I'm calling:
form = myforms.MyForm(request.POST, request.FILES)
if (form.is_valid()):
# do something
else:
# redisplay the form
How do I define MyForm to allow me to validate each aname and also, when in error, the widget to redisplay the above <input>s?
I can't figure out how to use the MultiValueField or even if it's the right thing to use. It seems to be a solution when you know how many fields you have?
Using clean_aname() in the form is no help as self.cleaned_data.get('aname') is only the last value.
Without the form, I would use something like request.POST.getlist('aname'), but I would like to avoid this if I can do it with django.forms.
Thanks for your help.
EDIT
I've left aside that I was defining more fields from a ModelForm. I think this might have some effects with formset. Here is where I am at... Is this solution considered to be "Django forms" compatible?
class MyField(forms.Field):
widget = MyWidget
def to_python(self, value):
if (isinstance(value, basestring)):
value = [value]
return [json.loads(v) for v in value]
class MyForm(forms.ModelForm):
class Meta:
model = models.MyModel
aname = MyField()
def clean(self):
cleaned_data = super(MyForm, self).clean()
cleaned_data['aname'] = self.fields['aname'].clean(self.data.getlist('aname'))
return cleaned_data
Now, I have to define MyWidget to allow me to display a list of <input type="hidden">, but I would like to know if this solution sound acceptable. Maybe I could have done this in clean_aname() too.

Answer 1

You could try implementing this using a set of forms (called formsets within Django), in which each form would be an instance of the validation form you want. For instance,
class ValidationForm(forms.Form):
aname = forms.CharField()
def clean_aname(self):
aname = self.cleaned_data['aname']
# TODO validate aname
return aname
def save(self, commit=False):
# TODO implement this form's save logic
return 'It works!'
For creating a set of those forms (see formset documentation), do:
from django.forms.formsets import formset_factory
ValidationFormSet = formset_factory(ValidationForm)
On your view, use the ValidationFormSet for receiving the data:
def my_view(request):
if request.method == 'POST':
form = ValidationFormSet(request.POST, request.FILES)
if form.is_valid():
# All anames were validated by clean_aname
results = form.save()
for r in results:
print r # Should print 'It works!'
else:
form = ValidationFormSet()
return <your_result>

Answer 2

You can pass multiple forms to your view using prefix, like this:
jsondumplist = ['jsondump1', 'jsondump2', 'jsondump3', 'jsondump4'....]
if request.method == 'POST':
forms = [YourForm(request.POST, prefix=x) for x in jsondumplist]
for f in forms:
if f.is_valid():
f.save()
else:
forms = [YourForm(prefix=x) for x in jsondumplist]
YourForm could have just the single field you are interested in, or several.
class YourForm(forms.Form):
aname = forms.CharField(widget=forms.HiddenInput())
Then, your template will look something like this:
{% for form in forms %}
{% for field in form %}
{{ field }}
{% endfor %}
{% endfor %}