How to get Interdependent dropdowns in django using Modelform and jquery?

You might need to use the following technologies:

• Custom Django Form Fields (Within the model form)
• ajax(to fetch the records)
• simplejson(to send a json response to ajax)
• jquery(to update the combo boxes on client side)

Let’s have a look at an example(Not really tested this, just from the top of my mind):

Models.py

from django.db import models

class Campus(models.Model):
    name = models.CharField(max_length=100, choices=choices.CAMPUSES)

    def __unicode__(self):
        return u'%s' % self.name

class School(models.Model):
    name = models.CharField(max_length=100)
    campus = models.ForeignKey(Campus)

    def __unicode__(self):
        return u'%s' % self.name

class Centre(models.Model):
    name = models.CharField(max_length=100)
    school = models.ForeignKey(School)

    def __unicode__(self):
        return u'%s' % self.name

Forms.py

import models
from django import forms

class CenterForm(forms.ModelForm):
    campus = forms.ModelChoiceField(queryset=models.Campus.objects.all())
    school = forms.ModelChoiceField(queryset=models.School.objects.none()) # Need to populate this using jquery
    centre = forms.ModelChoiceField(queryset=models.Centre.objects.none()) # Need to populate this using jquery

    class Meta:
        model = models.Center

        fields = ('campus', 'school', 'centre')

Now, write a method in your views that returns a json object for schools under a campus and centres under a school:

Views.py

import models
import simplejson
from django.http import HttpResponse

def get_schools(request, campus_id):
    campus = models.Campus.objects.get(pk=campus_id)
    schools = models.School.objects.filter(campus=campus)
    school_dict = {}
    for school in schools:
        school_dict[school.id] = school.name
    return HttpResponse(simplejson.dumps(school_dict), mimetype="application/json")

def get_centres(request, school_id):
    school = models.School.objects.get(pk=school_id)
    centres = models.Centre.objects.filter(school=school)
    centre_dict = {}
    for centre in centres:
        centre_dict[centre.id] = centre.name
    return HttpResponse(simplejson.dumps(centre_dict), mimetype="application/json")

Now write a ajax/jquery method to fetch the data and populate the select elements in the HTML.

AJAX/jQuery

$(document).ready(function(){
    $('select[name=campus]').change(function(){
        campus_id = $(this).val();
        request_url="/get_schools/" + campus_id + "https://stackoverflow.com/";
        $.ajax({
            url: request_url,
            success: function(data){
                $.each(data, function(index, text){
                    $('select[name=school]').append(
                         $('<option></option>').val(index).html(text)
                     );
                });
            }
        });
        return false;
    })
});