handle a huge list of ForeignKey objects by implementing a CategorizedModelChoiceField

[ulda]

Think of having a model like this:

PRKAT_CHOICES= (
    ('M','Metrisch'),
    ('MF', 'Metrisch-Fein'),
#   some more here left out for shortness...
)
class Profil(models.Model):
    kategorie=models.CharField('Kategorie',maxlength=4,choices=PRKAT_CHOICES)
    bezeichnung=models.CharField('Bezeichnung',maxlength=30)

and your database fills up with profile objects in hundreds with different categories.

Now another model is calling this model like

class Karte(models.Model):
	ba_nr=models.PositiveIntegerField("BA-Nr",primary_key=True)
	datum=models.DateField("Datum",default=date.today)

	profil=ForeignKey(Profil)

and in your forms for Karte you get an ugly select filling the screen.

Attached you find a CategorizedModelChoiceField. With this in hand, you subclass ForeignKey to your model specific ProfileKey

class ProfilKey(models.ForeignKey):
    def formfield(self,**kwargs):
        defaults = {'form_class': CategorizedModelChoiceField, 'queryset': self.rel.to._default_manager.all(), 'category': 'kategorie' , 'callback_link': '/pr/list_of_profiles_for_category/'}
        defaults.update(kwargs)
        return super(ProfilKey, self).formfield(**defaults)

and change the ForeignKey definition in your other model to

	profil=ProfileKey(Profil)

Because the whole thing works with a simple kind of ajax, you need a callback function in your urls like this:

urlpatterns = patterns('myproject.categorizedmodelchoicefield',
    (r'^pr/list_of_profiles_for_category/$','get_choices_for_category',
     { 'queryset': Profil.objects.all(),
       'category_name':'kategorie' } ),
)

and voilais: in your forms for Karte you get two selects for category and the actual choice value which updates according to the users selection.

you may also use the formfield_callback but why not using the objects if they are handy...

making it work you need:

• CategorizedModelChoiceField.py attached
• JsonResponse from djangosnipplets.org
• http.Request form openjsan.org loaded somewhere in your base templates

I think something like this should be included as example extension to newforms and to using django/json/ajax. therefore i didn't post ant djangosnipplets.

the javascript code maybe looks ugly, but this is because it was the first time i did javascript.

[James Bennett]

The JS in this patch seems to require some third-party toolkit to work properly; tying Django to a JavaScript library is not something we're interested in doing.

[Aymeric Augustin]

Change UI/UX from NULL to False.

[Aymeric Augustin]

Change Easy pickings from NULL to False.

[Aymeric Augustin]

The implementation is very far from Django's current standards, and it doesn't need to live in core.

Besides, demand for this feature is non-existent: there hasn't been a single commend here in 6 years.