django-enum-choices 0.0.6

A custom Django field able to use subclasses of Python's internal `Enum` class as choices

django-enum-choices

Library is still work in progress & unstable. When officially launched, we'll announce it.

A custom Django choice field to use with Python enums.

Installation

pip install django_enum_choices

Basic Usage

from django import models

from django_enum_choices.fields import EnumChoiceField


from enum import Enum

class FooBarEnumeration(Enum):
    FOO = 'foo'
    BAR = 'bar'


class MyModel(models.Model):
    foo_bar_field = EnumChoiceField(FooBarEnumeration)

Model creation

instance = MyModel.objects.create(foo_bar_field=FooBarEnumeration.BAR)

Changing enum values

instance.foo_bar_field = FooBarEnumeration.FOO
instance.save()

Filtering

MyModel.objects.filter(foo_bar_field=FooBarEnumeration.FOO)

Usage with Django Rest Framework

from rest_framework import serializers

from django_enum_choices.serializers import EnumChoiceField

class MyModelSerializer(serializers.ModelSerializer):
    foo_bar_field = EnumChoiceField(FooBarEnumeration)

    class Meta:
        model = MyModel
        fields = ('foo_bar_field', )

In python manage.py shell:

In [1]: instance = MyModel.objects.create(foo_bar_field=FooBarEnumeration.BAR)
In [2]: MyModelSerializer(instance).data
Out[2]: {'foo_bar_field': 'bar'}

Caveat

If you don't explicitly specify the foo_bar_field = EnumChoiceField(FooBarEnumeration), then you need to include the EnumChoiceModelSerializerMixin:

from rest_framework import serializers

from django_enum_choices.serializers import EnumChoiceModelSerializerMixin

class MyModelSerializer(EnumChoiceModelSerializerMixin, serializers.ModelSerializer):
    class Meta:
        model = MyModel
        fields = ('foo_bar_field', )

By default ModelSerializer.build_standard_field coerces any field that has a model field with choices to ChoiceField wich returns the value directly.

Since enum values resemble EnumClass.ENUM_INSTANCE they won't be able to be encoded by the JSONEncoder when being passed to a Response.

That's why we need the mixin.

Implementation details

• EnumChoiceField is a subclass of CharField.
• Only subclasses of Enum are valid arguments for EnumChoiceField.
• choices are generated from the values of the enumeration, like (str(value), str(value)), meaning you can put any valid Python object there.
• max_length, if passed, is ignored. max_length is automatically calculated from the longest choice.

For example, lets have the following case:

class Value:
    def __init__(self, value):
        self.value = value

    def __str__(self):
        return str(self.value)


class Enumeration(Enum):
    A = Value(1)
    B = Value('foo')


class SomeModel(models.Model):
    enumeration = EnumChoiceField(Enumeration)

We'll have the following:

• SomeModel.enumeration.choices == (('1', '1'), ('foo', 'foo'))
• SomeModel.enumeration.max_length == 3

Development

git clone https://github.com/HackSoftware/django-enum-choices.git
pip install -e some-directory/django_enum_choices