How to overide django modelform to achieve custom behaviour - django

Question

I have an Item object that has a manytomany relation to another object Option. I create a modelform from the Item object like so;
class Item(models.Model):
category = models.ForeignKey(Category)
name = models.CharField(max_length=200)
price = models.DecimalField(max_digits=9, decimal_places=2, blank=True, null=True)
options = models.ManyToManyField(Option)
class OptionForm(ModelForm):
options = forms.ChoiceField(widget=forms.RadioSelect())
class Meta:
model = Item
fields = ( 'options', )
When i render the form in the template it renders all available options for the Item object(the expected behavior) even those not created by a specific item. I want to be able to load options defined by the specific Item that will be chosen by the user. How do i override the form to achieve such behavior.for example without a form i can render an Items own Options through its id. item = Item.objects.get(pk=id)

Answer 1

Its tough to make ModelForm's defined on the fly because they are intimately tied to the structure in your model. Nevertheless you could use some clever template control flow and view rendering to get your desired effect. This is untested so you millage with this might vary.
<form method="post" action="">
{{ formset.management_form }}
{% for form in formset %}
{{ form.id }}
<ul>
{% if user_option.category %}
<li>{{ form.caregory }}</li>
{% endif %}
{% if user_option.name %}
<li>{{ form.name }}</li>
{% endif %}
{% if user_option.p_opt %}
<li>{{ form.price }}</li>
<li>{{ form.options }}</li>
{% endif %}
</ul>
{% endfor %}
</form>
From the Djano docs here.

Answer 2

Try overriding the form's init method and passing in the Item pk as an additional argument. The trick here is to pop the argument before calling the parent init.
class ItemOptionsForm(forms.ModelForm):
class Meta:
model = Item
def __init__(self, *args, **kwargs):
# pop 'item_id' as parent's init is not expecting it
item_id = kwargs.pop('item_id', None)
# now it's safe to call the parent init
super(ItemOptionsForm, self).__init__(*args, **kwargs)
# Limit options to only the item's options
if item_id:
try:
item = Item.objects.get(id=item_id)
except:
raise ValidationError('No item found!')
self.fields['options'] = forms.ChoiceField(item.options)
Then, in your view, create the form like:
form = ItemOptionsForm(item_id=item_id)
The nice thing about this is that you can raise ValidationErrors that will show up in the form.
Be aware that this doesn't prevent someone from POSTing option IDs to your form which do not belong to the Item, so you'll likely want to override the ModelForm.clean() to validate the options as well.

Answer 3

learning from link django: How to limit field choices in formset? provided by #jingo, i solved the problem by first of all creating dynamic form like so;
def partial_order_item_form(item):
"""dynamic form limiting optional_items to their items"""
class PartialOrderItemform(forms.Form):
quantity = forms.IntegerField(widget=forms.TextInput(attrs={'size':'2', 'class':'quantity','maxlength':'5'}))
option = forms.ModelChoiceField(queryset=OptionalItems.objects.filter(item=item),widget= forms.RadioSelect())
return PartialOrderItemform
then validating form like so;
def show_item(request,id):
option = get_object_or_404(Item,pk=id)
if request.method == 'POST':
form = partial_order_item_form(option)
#bound form to POST data,
final_form = form(request.POST)
# check validation of posted data
if final_form.is_valid():
order.add_to_order(request)
url =urlresolvers.reverse('order_index',kwargs={'id':a.id})
# redirect to order page
return HttpResponseRedirect(url)
else:
form = partial_order_item_form(item=id)
context={
'form':form,
}
return render_to_response('item.html',context,context_instance=RequestContext(request))