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We must learn to live together as brothers or perish together as fools. “Martin Luther King, Jr“

Django grouped select field for ModelChoiceField or ModelMultipleChoiceField

Django forms’s builtin fields like ChoiceField, ModelChoiceField use by default forms.Select widget, but what we do if we need a Select with grouped options.

I found this awesome snippets that’s helped me to achieve this, just in my case I needed to add a line of code to show only options with parent.

Example

Here’s a model example:

    class Category(models.Model):

        name = models.CharField(max_length=100)
        parent = models.ForeignKey('self', null=True, blank=True)

        def __unicode__(self):
            return u'{0}'.format(self.name)

I created a form that use this model:

    class ExampleForm(forms.Form):

        category = GroupedModelChoiceField(
            label=_('Category'),
            group_by_field='parent',
            queryset=Category.objects.all(),
        )

The snippet show categories with None label, I don’t need to make user able to select Categories, only childs can be selected. So, I just edited the line 50 of the snippet to remove group categories.

    from itertools import groupby

    from django.forms.models import ModelChoiceIterator, ModelChoiceField


    class GroupedModelChoiceField(ModelChoiceField):

        def __init__(self, group_by_field, group_label=None, *args, **kwargs):
            """
            group_by_field is the name of a field on the model
            group_label is a function to return a label for each choice group
            """
            super(GroupedModelChoiceField, self).__init__(*args, **kwargs)
            self.group_by_field = group_by_field
            if group_label is None:
                self.group_label = lambda group: group
            else:
                self.group_label = group_label

        def _get_choices(self):
            """
            Exactly as per ModelChoiceField except returns new iterator class
            """
            if hasattr(self, '_choices'):
                return self._choices
            return GroupedModelChoiceIterator(self)
        choices = property(_get_choices, ModelChoiceField._set_choices)


    class GroupedModelChoiceIterator(ModelChoiceIterator):

        def __iter__(self):
            if self.field.empty_label is not None:
                yield (u"", self.field.empty_label)
            if self.field.cache_choices:
                if self.field.choice_cache is None:
                    self.field.choice_cache = [
                        (self.field.group_label(group), [
                         self.choice(ch) for ch in choices])
                        for group, choices in groupby(
                            self.queryset.all(),
                            key=lambda row: getattr(row, self.field.group_by_field))
                    ]
                for choice in self.field.choice_cache:
                    yield choice
            else:
                for group, choices in groupby(
                        self.queryset.all(),
                        key=lambda row: getattr(
                            row, self.field.group_by_field)):
                    if group is not None: #Line added
                        yield (
                            self.field.group_label(group),
                            [self.choice(ch) for ch in choices])

Okay, now this custom field work, but what if I need a grouped select multiple with ModelMultipleChoiceField ?

We can just add a new field like GroupedModelChoiceField that inherits from ModelMultipleChoiceField

    from django.forms.models import ModelMultipleChoiceField


    class GroupedMultipleModelChoiceField(ModelMultipleChoiceField):

        def __init__(self, group_by_field, group_label=None, *args, **kwargs):
            """
            group_by_field is the name of a field on the model
            group_label is a function to return a label for each choice group
            """
            super(GroupedMultipleModelChoiceField, self).__init__(*args, **kwargs)
            self.group_by_field = group_by_field
            if group_label is None:
                self.group_label = lambda group: group
            else:
                self.group_label = group_label

        def _get_choices(self):
            """
            Exactly as per ModelChoiceField except returns new iterator class
            """
            if hasattr(self, '_choices'):
                return self._choices
            return GroupedModelChoiceIterator(self)
        choices = property(_get_choices, ModelMultipleChoiceField._set_choices)

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