Argument of type 'NoneType' is not iterable with ModelForm

Question

I'm getting the following error when trying to submit a form:

argument of type 'NoneType' is not iterable

My form class is as follows:

class requestform(ModelForm):
def __init__(self, *args, **kwargs):
    super(requestform, self).__init__(*args,**kwargs)
    self.is_update=False
requestedpart = forms.CharField (label="Requested Part", max_length=80, required= True)
librarytype = forms.TypedChoiceField (label="Type", choices = ((1, "Type1"), (2, "Type2"), (3, "Type3")), coerce = lambda x: bool(int(x)), widget = forms.RadioSelect, required= True)
requestformat = forms.TypedChoiceField (label="Format", choices = ((1, "Format1"), (2, "Format2")), coerce = lambda x: bool(int(x)), widget = forms.RadioSelect, required= True)
def clean(self):
    if 'requestedpart' not in self.cleaned_data:
        return
    if not self.is_update:
        return self.cleaned_data
class Meta:
    model = LibraryRequest

My views is as follows

if request.method == "POST":
    formtoaddrequest = requestform(request.POST, request.FILES)
    if requestform.is_valid(formtoaddrequest):
        new_request = formtoaddrequest.save(commit=False)
        new_request.requestadder = request.user 
        new_request.save()
        request.user.message_set.create(message=_("You have saved '%(requestedpart)s'") %  {'requestedpart': new_request.requestedpart})

Here's my traceback

Traceback:
File "/Users/AB/Desktop/myenv2/lib/python2.7/site-packages/django/core/handlers/base.py" in get_response
  100.                     response = callback(request, *callback_args, **callback_kwargs)
File "/Users/AB/Desktop/store/project/views.py" in view_requests
  201.          if formtoaddmodel.is_valid():
File "/Users/AB/Desktop/myenv2/lib/python2.7/site-packages/django/forms/forms.py" in is_valid
  121.         return self.is_bound and not bool(self.errors)
File "/Users/AB/Desktop/myenv2/lib/python2.7/site-packages/django/forms/forms.py" in _get_errors
  112.             self.full_clean()
File "/Users/AB/Desktop/myenv2/lib/python2.7/site-packages/django/forms/forms.py" in full_clean
  269.         self._post_clean()
File "/Users/AB/Desktop/myenv2/lib/python2.7/site-packages/django/forms/models.py" in _post_clean
  316.         self.instance = construct_instance(self, self.instance, opts.fields, opts.exclude)
File "/Users/AB/Desktop/myenv2/lib/python2.7/site-packages/django/forms/models.py" in construct_instance
  40.                 or not f.name in cleaned_data:

Exception Type: TypeError at /project/view_requests/
Exception Value: argument of type 'NoneType' is not iterable

Any insight into why I might be getting this error?

Answer 1

There are multiple issues.

Your clean method should either raise a ValidationError or return self.cleaned_data. Your clean() method does not raise error but returns None, change is to as below:

def clean(self):
    if self.cleaned_data and 'requestedpart' not in self.cleaned_data:
        raise forms.ValidationError("Some error message")
    if not self.is_update:
        return self.cleaned_data
    return self.cleaned_data

Similarly, if you have clean_fieldname for a field fieldname, return its value:

def clean_fieldname(self):
    # ...
    return self.cleaned_data['fieldname']

You can also check if self.cleaned_data is non-null

In your view, form validation should be like: if requestform.is_valid() ie. without parameters.