Better ArrayField admin widget?

I take no credit for this (original source), but if you are using PostgreSQL as the database and are happy to use the Postgres-specific ArrayField implementation there is an even easier option: subclass ArrayField on the model and override the default admin widget. A basic implementation follows (tested in Django 1.9, 1.10, 1.11, 2.0, 2.1 & 2.2):

models.py

from django import forms
from django.db import models
from django.contrib.postgres.fields import ArrayField


class ChoiceArrayField(ArrayField):
    """
    A field that allows us to store an array of choices.
    Uses Django's Postgres ArrayField
    and a MultipleChoiceField for its formfield.
    """

    def formfield(self, **kwargs):
        defaults = {
            'form_class': forms.MultipleChoiceField,
            'choices': self.base_field.choices,
        }
        defaults.update(kwargs)
        # Skip our parent's formfield implementation completely as we don't
        # care for it.
        # pylint:disable=bad-super-call
        return super(ArrayField, self).formfield(**defaults)


FUNCTION_CHOICES = (
    ('0', 'Planning'),
    ('1', 'Operation'),
    ('2', 'Reporting'),
)


class FunctionModel(models.Model):
    name = models.CharField(max_length=128, unique=True)
    function = ChoiceArrayField(
        base_field=models.CharField(max_length=256, choices=FUNCTION_CHOICES),
        default=list)