Question

I have a Location model and an associated form that displays the “location” field as a bunch of radio buttons (using the form queryset to display the values). There are a small number of locations, but they need to be dynamic. I’d like to display the location description next to each radio box option so users have a bit more info on the locations.

Pretend this is a list of radio buttons, this is what I’d like it to look like:

<> East – This location is east. <> West – This is the west location! <> North – This is the north location

I have a model similar to the following:

class Location(models.Models):
    location = models.CharField(max_length=50)
    description = models.TextField(blank=True, null=True)

And a form as such:

class LocationForm(forms.Form):
    location = ExtraModelChoiceField(
               widget=RadioSelect(renderer=ExtraHorizRadioRenderer), 
               queryset = models.Locations.objects.filter(active=True))

I can’t seem to find a good way to render the form so I can display the description along with each select option. I’ve done a lot of overriding, but am not having too much luck.

MY ATTEMPT TO SOLVE (BUT NO LUCK YET):

From what I gather, normally if a queryset is provided on the form field, the Django form logic translates that into a choices tupal of tupals. Each “subtupal” contains an id and label that is displayed when it is rendered. I’m trying to add a third value to those “subtupals” which would be a description.

I’ve defined a custom renderer to display my radio buttons horizontally and to pass in my custom choices.

class ExtraHorizRadioRenderer(forms.RadioSelect.renderer):
    def render(self):
        return mark_safe(u'\n'.join([u'%s\n' % w for w in self]))

    def __iter__(self):
        for i, choice in enumerate(self.choices):
            yield ExtraRadioInput(self.name, self.value, 
                                  self.attrs.copy(), choice, i)

    def __getitem__(self, idx):
        choice = self.choices[idx] # Let the IndexError propogate
        return ExtraRadioInput(self.name, self.value, 
                               self.attrs.copy(), choice, idx)

I’ve overridden the Django RadioInput class so I can add the description information that I need to display next to the Radio Buttons.

class ExtraRadioInput(forms.widgets.RadioInput):

    def __init__(self, name, value, attrs, choice, index):
        self.name, self.value = name, value
        self.attrs = attrs
        self.choice_value = force_unicode(choice[0])
        self.choice_label = force_unicode(choice[1])
        self.choice_description = force_unicode(choice[2])   # <--- MY ADDITION; FAILS
        self.index = index

    def __unicode__(self):
        if 'id' in self.attrs:
            label_for = ' for="%s_%s"' % (self.attrs['id'], self.index)
        else:
            label_for = ''
        choice_label = conditional_escape(force_unicode(self.choice_label))
        return mark_safe(u'<label%s>%s %s</label>' % (
             label_for, self.tag(), choice_label))

    def tag(self):
        if 'id' in self.attrs:
            self.attrs['id'] = '%s_%s' % (self.attrs['id'], self.index)
        final_attrs = dict(self.attrs, type='radio', name=self.name, 
                      value=self.choice_value)
        if self.is_checked():
            final_attrs['checked'] = 'checked'
        return mark_safe(
           u'<input%s /><span class="description">%s</span>' % \
           (flatatt(final_attrs),self.choice_description ))  # <--- MY ADDTIONS

I’ve also overridden the following two Django classes hoping to pass around my modified choices tupals.

class ExtraModelChoiceIterator(forms.models.ModelChoiceIterator  ):    

    def choice(self, obj): 
        if self.field.to_field_name:
            key = obj.serializable_value(self.field.to_field_name)
        else:
            key = obj.pk

        if obj.description:   # <-- MY ADDITIONS
            description = obj.description
        else:
            description = ""
        return (key, self.field.label_from_instance(obj),description)


class ExtraModelChoiceField(forms.models.ModelChoiceField):

    def _get_choices(self):
        if hasattr(self, '_choices'):
            return self._choices
        return ExtraModelChoiceIterator(self)  # <-- Uses MY NEW ITERATOR

Using the approach above, I can’t seem to be able to pass around my 3-value tupal. I get a “tuple index out of range” failure (up where I mark FAILURE above) indicating that somehow my tupal does not have the extra value.

Does anyone see a flaw in my logic, or more generally have an approach to displaying a description next to a list of choices using a widget?

Thanks for reading. Any comments are much appreciated.
Joe

Answer 1

Sorry to answer my own question, but I think I have a method to do this. As always, it appears to be simpler than I was making it before. Overriding the label_from_instance method on an extended ModelChoiceField seems to allow me to access the model object instance to be able to print out extra information.

from django.utils.encoding import smart_unicode, force_unicode

class ExtraModelChoiceField(forms.models.ModelChoiceField):

    def label_from_instance(self, obj):
        return mark_safe(
            "<span>%s</span><span class=\"desc\" id=\"desc_%s\">%s</span>" % (
            mart_unicode(obj), obj.id, smart_unicode(obj.description),))


class HorizRadioRenderer(forms.RadioSelect.renderer):
    # for displaying select options horizontally. 
    # https://wikis.utexas.edu/display/~bm6432/Django-Modifying+RadioSelect+Widget+to+have+horizontal+buttons
    def render(self):
        return mark_safe(u'\n'.join([u'%s\n' % w for w in self]))


class LocationForm(forms.Form):
    location = ExtraModelChoiceField(widget=forms.RadioSelect(renderer=HorizRadioRenderer),
        queryset=models.Location.objects.filter(active=True))

If you know of a better approach, I’d be excited to see it. Otherwise, this will have to do. Thanks for reading. Hope this saves someone the frustration I had.

Joe