Django options field with categories

Question

I have the following code in my models.py(removed irrelevant fields):

class Choices(models.Model):
    name = models.CharField(max_length=300)
    choice_type = models.CharField(max_length=200)

    def __unicode__(self):
        return self.name

class UserProfile(models.Model):
    user = models.ForeignKey(User, unique=True)
    planguages = models.ManyToManyField(Choices)

and my utils.py(originaly from django-profiles, that's parsing forms):

def get_profile_form():
    profile_mod = get_profile_model()
    class _ProfileForm(forms.ModelForm):
        planguages = forms.ModelMultipleChoiceField(queryset=Choices.objects.all(), required=False, widget=forms.CheckboxSelectMultiple)

        class Meta:
            model = profile_mod
            exclude = ('user',) # User will be filled in by the view.
    return _ProfileForm

Now, what I'd like to do is to have a table Choices, that will have the name and choice_type columns, which I already have. The problem is that I don't really know how can I tie an option to a category, and make a user, when they're creating their profile, pick an programming language or a framework, based on choice in choice_type.

I assume it'd involve some JS, but that's not as much of a problem as django code.

Answer 1

You're going to want to make these actual models, so you'd have something like this:

class ProgrammingCategory(models.Model):
    name = models.CharField(max_length=200)

class ProgrammingLanguage(models.Model):
    category = models.ForeignKey(ProgrammingCategory, related_name='languages')
    name = models.CharField(max_length=300)

class UserProfile(models.Model):
    user = models.ForeignKey(User, unique=True)
    planguages = models.ManyToManyField(ProgrammingLanguage)

Not only is this better from a maintainability standpoint (programming languages do change: new ones come around, old ones die out), but it also gives you much greater flexibility in querying.

Then, you simply add a field to your ModelForm for the categories:

class UserProfileForm(forms.ModelForm):
    ...
    category = forms.ModelChoiceField(queryset=ProgrammingCategory.objects.all(), required=False)

And, in your form, you'll end up with a select with a complete list of categories and another with a complete list of languages. Then, all you need is some AJAX to do the filtering for you:

views.py

from django.core import serializers
from django.http import HttpResponse, HttpResponseBadRequest

def ajax_get_languages_for_category(request):
    cat_id = request.GET.get('cat_id')
    if cat_id is not None:
        category = get_object_or_404(ProgrammingCategory, id=cat_id)
        data = serializers.serialize('json', category.languages.all())
        return HttpResponse(data, mimetype='application/json')
    else:
        return HttpResponseBadRequest()

script.js

$(document).ready(function(){
    var $category = $('#id_category');
    function updateLanguageChoices() {
        var selected = $category.val();
        if (selected) {
            $.getJSON('/path/to/ajax/view/', { cat_id: selected }, function (data, jqXHR) {
                var output = [];
                $.each(data, function(i, item){
                    output.append('<option value="'+item.id+'">'+item.name+'</option>');
                });
                $('#id_planguage').html(output.join(''));
            });
        }
    }
    updateLanguageChoices();
    $category.change(updateLanguageChoices);
});