How do I change a form value in Django? - django

Question

We are using Django 1.4.3 with django-cities-light 2.1.5 to create our website. We are using the form's __init__ method to update the lists of regions and cities. The problem is that if the user selected a city and the form doesn't validate, I want to change the region selection to the region of the selected city. Here is the code:
def __init__(self, instance, *args, **kwargs):
super(ContentItemModelForm, self).__init__(*args, instance=instance, **kwargs)
....
....
....
country_id = None
if ((hasattr(self, "initial")) and ("country_id" in self.initial)):
country_id = int(self.initial['country_id']) if self.initial['country_id'] else None
elif ((hasattr(self, "data")) and (u'country_id' in self.data)):
country_id = int(self.data[u'country_id']) if self.data[u'country_id'] else None
region_id = None
if ((hasattr(self, "initial")) and ("region_id" in self.initial)):
region_id = int(self.initial['region_id']) if self.initial['region_id'] else None
elif ((hasattr(self, "data")) and (u'region_id' in self.data)):
region_id = int(self.data[u'region_id']) if self.data[u'region_id'] else None
city_id = None
if ((hasattr(self, "initial")) and ("city_id" in self.initial)):
city_id = int(self.initial['city_id']) if self.initial['city_id'] else None
elif ((hasattr(self, "data")) and (u'city_id' in self.data)):
city_id = int(self.data[u'city_id']) if self.data[u'city_id'] else None
if (city_id):
city_obj = City.objects.get(geoname_id=city_id)
country_id = city_obj.country_id
region_id = city_obj.region_id
# Set current values of country_id and region_id - commented (not working).
#self.fields['country_id'].initial = country_id
#self.fields['region_id'].initial = region_id
self.fields['region_id'].choices = [("", "(None)", ),]+[(obj.id, obj.name) for obj in Region.objects.filter(country_id=country_id).order_by("name")]
if (region_id):
self.fields['city_id'].choices = [("", "(None)", ),]+[(obj.geoname_id, obj.name) for obj in City.objects.filter(country_id=country_id, region_id=region_id).order_by("name")]
else:
self.fields['city_id'].choices = [("", "(None)", ),]+[(obj.geoname_id, obj.name) for obj in City.objects.filter(country_id=country_id).order_by("name")]
The code that checks the current values of city_id, region_id and country_id is too long and I didn't find a way to shorten it. And the commented lines (self.fields['country_id'].initial = country_id and self.fields['region_id'].initial = region_id) don't work if they are not commented - if only country and city are selected then the selected region is "(None)" (if the form does not validate). If the form validates then we assign the country_id and region_id values according to the selected city (the country and region are not saved to the database).
Here is the city validation:
def clean_city_id(self):
cleaned_data = self.cleaned_data
country_id = cleaned_data['country_id'] if (cleaned_data.has_key('country_id')) else None
region_id = cleaned_data['region_id'] if (cleaned_data.has_key('region_id')) else None
city_id = cleaned_data['city_id'] if (cleaned_data.has_key('city_id')) else None
if (not(city_id)):
if (region_id):
error_message = "If you select a country and a state/region, you must select a city."
self._errors["city_id"] = self.error_class([error_message])
raise forms.ValidationError(error_message)
elif (country_id):
error_message = "If you select a country, you must select a city."
self._errors["city_id"] = self.error_class([error_message])
raise forms.ValidationError(error_message)
return city_id
Do you know how do we assign the correct values to the country and region?
(Edit): We want to have selected="selected" in the HTML in the correct region after a city is selected, and not in the first "(None)" region (also if the user didn't select a region). We use AJAX to update the lists after the user selects a new country or region, but we don't want to use AJAX immediately after loading the form.
Thanks,
Uri.

Answer 1

I would suggest alternative way to solve the problem. Alternative to "manually" setting values for user - let user do it itself. Like this:
1) Trigger form GET on select change event
2) in those event callbacks pass form data to view - just like you do with POST. Just do GET request not POST request.
3) In view just pass request.GET as first parameter to form instead of request.POST
4) Let your existing logic do the magic in form init method.
5) Return form template with correct and valid choices from view
6) switch existing form with new form.
Thats how i would do it anyway. No need to assign anything. Let user do the choices they can after refreshing the form.