form.is_valid method keeps failing - django

Question

I'm trying to make an editing page for the users to update an object data. However, form.is_valid() keeps failing, I have no idea why.
My model:
class Thread(models.Model):
title = models.CharField(max_length=200)
created = models.DateTimeField(auto_now_add=True)
creator = models.ForeignKey(User, blank=True, null=True)
body = models.TextField(max_length=10000)
USER_TYPES = (
('INI','Iniciante'),
('INT','Intermediário'),
('AVA','Avançado')
)
user_type = models.CharField(max_length=20, choices = USER_TYPES, default='INI')
category = models.ForeignKey(Category)
orcamento = models.IntegerField(default=0)
slug = models.SlugField(max_length=40, unique=True)
def get_absolute_url(self):
return "/%s/" % self.slug
def __str__(self):
return self.title
def save(self, **kwargs):
slug_str = "%s %s" % (self.category, self.title)
unique_slugify(self, slug_str)
super(Thread, self).save(**kwargs)
My view:
def edit_thread(request, thread_slug):
thread = Thread.objects.get(slug=thread_slug)
if request.method == 'POST':
form = EditThread(request.POST)
if form.is_valid():
thread.title = form.cleaned_data['title']
thread.orcamento = form.cleaned_data['orcamento']
thread.user_type = form.cleaned_data['experiencia']
thread.body = form.cleaned_data['pergunta']
thread.save()
return HttpResponseRedirect('/thread' + thread.get_absolute_url())
else:
data = {'title' : thread.title, 'experiencia':thread.user_type, 'orcamento' : thread.orcamento, 'pergunta': thread.body}
form = EditThread(initial=data)
return render(request, 'edit_thread.html', {
'form': form })
My form:
class EditThread(forms.ModelForm):
title = forms.CharField(label='Título', max_length=200, error_messages=my_default_errors)
orcamento = forms.IntegerField(label='Preço máximo', error_messages=my_default_errors)
experiencia = forms.ChoiceField(label='Você é um usuário...', choices=Thread.USER_TYPES, error_messages=my_default_errors)
pergunta = forms.CharField(label='Pergunta', widget=forms.Textarea, error_messages=my_default_errors)
class Meta:
model = Thread
def __init__(self, *args, **kwargs):
super(EditThread, self).__init__(*args, **kwargs)
self.helper = FormHelper(self)
self.helper.layout = Layout(
Div('title',
'experiencia',
PrependedAppendedText('orcamento', 'R$', ',00', active=True),
'pergunta',
FormActions(
Submit('save', 'Salvar alterações'),
)))
When accessing the page, the form gets pre-populated with the object's data as it should.

Answer 1

Your form should be inherited from the simple forms.Form instead of the forms.ModelForm:
class EditThread(forms.Form):
...

Answer 2

I would suggest you look at django's class based UpdateView. It can generate an update form for you or you could give it a custom ModelForm by overriding the form_class attribute on your view. When using a ModelForm, you also have to specify which model the form is for eg:
class EditThread(forms.ModelForm):
"field definitions ..."
class Meta:
model = Thread
fields = ['my_field_1', 'my_field_2']