Django ModelForm with field overwrite does not post data - django

Question

So, I have the following form:
class DesignItemForm (forms.ModelForm):
def __init__(self, *args, **kwargs):
super(DesignItemForm, self).__init__(*args, **kwargs)
CHOICES=[(i,i) for i in range(MAX_DESIGN_ITEM_QUANTITY)]
self.fields['quantity'] = forms.ChoiceField(choices=CHOICES)
class Meta:
model = DesignItem
fields = ('quantity','trackable',)
My view:
d = Design.object.get(slug=fromInput)
....
DesignItemInlineFormSet = inlineformset_factory(Design, DesignItem, fk_name="design", form=DesignItemForm,)
if request.method == "POST":
formset = DesignItemInlineFormSet(request.POST, request.FILES, instance=d)
if formset.is_valid():
formset.save()
DesignItemInlineFormSet(instance=d)
As you can tell, in my form, I overwrote the quantity field to be a drop down instead of an integer field.
For some reason, when I submit the form, the data is not updated in the database. However, if I change the form to the following, it works (of course, it doesn't have the dropdowns I want, but it posts to the db). Why is this, and how do I fix it?
class DesignItemForm (forms.ModelForm):
def __init__(self, *args, **kwargs):
super(DesignItemForm, self).__init__(*args, **kwargs)
# CHOICES=[(i,i) for i in range(MAX_DESIGN_ITEM_QUANTITY)]
# self.fields['quantity'] = forms.ChoiceField(choices=CHOICES)
class Meta:
model = DesignItem
fields = ('quantity','trackable',)
EDIT: Here is the DesignItem model:
class DesignItem(models.Model):
"""Specifies how many of an item are in a design."""
design = models.ForeignKey(Design, related_name="items")
quantity = models.PositiveIntegerField(default=1)
trackable = models.ForeignKey(Trackable, related_name="used")

Answer 1

have you tried just overriding the widget instead of the whole field?
i guess you want a select widget
def __init__(self, *args, **kwargs):
super(DesignItemForm, self).__init__(*args, **kwargs)
CHOICES=[(i,i) for i in range(MAX_DESIGN_ITEM_QUANTITY)]
self.fields['quantity'].widget = forms.Select(choices=CHOICES)