ORM integration

.travis.yml

@@ -2,29 +2,27 @@ language: python
 cache: pip
 sudo: false
 
-python: 
+python:
   - "2.7"
   - "3.4"
   - "3.5"
   - "3.6"
 
 env:
-  - DJANGO=1.8
-  - DJANGO=1.9
-  - DJANGO=1.10
   - DJANGO=1.11
   - DJANGO=2.0
   - DJANGO=2.1
+  - DJANGO=2.2
 
 matrix:
   fast_finish: true
   exclude:
     - { python: "2.7", env: DJANGO=2.0 }
     - { python: "2.7", env: DJANGO=2.1 }
+    - { python: "2.7", env: DJANGO=2.2 }
+
     - { python: "3.4", env: DJANGO=2.1 }
-    - { python: "3.6", env: DJANGO=1.8 }
-    - { python: "3.6", env: DJANGO=1.9 }
-    - { python: "3.6", env: DJANGO=1.10 }
+    - { python: "3.4", env: DJANGO=2.2 }
 
 install:
   - pip install coverage coveralls tox tox-travis

djchoices/choices.py

@@ -4,6 +4,7 @@
 from collections import OrderedDict
 
 from django.core.exceptions import ValidationError
+from django.db.models import Case, IntegerField, Value, When
 from django.utils import six
 from django.utils.deconstruct import deconstructible
 
@@ -195,3 +196,30 @@ def get_choice(cls, value):
         """
         attribute_for_value = cls.attributes[value]
         return cls._fields[attribute_for_value]
+
+    @classmethod
+    def get_order_expression(cls, field_name):
+        """
+        Build the Case/When to annotate objects with the choice item order
+
+        Useful if choices represent some access-control mechanism, for example.
+
+        Usage::
+
+        >>> order = MyChoices.get_order_expression('some_field')
+        >>> queryset = Model.objects.annotate(some_field_order=order)
+        >>> for item in queryset:
+        ...     print(item.some_field)
+        ...     print(item.some_field_order)
+        # first_choice
+        # 1
+        # second_choice
+        # 2
+        """
+        whens = []
+        for choice_item in cls._fields.values():
+            whens.append(When(**{
+                field_name: choice_item.value,
+                "then": Value(choice_item.order)
+            }))
+        return Case(*whens, output_field=IntegerField())

djchoices/tests/test_choices.py

@@ -1,5 +1,7 @@
 import unittest
 
+from django.db.models import Case, IntegerField, Value, When
+
 from djchoices import C, ChoiceItem, DjangoChoices
 
 
@@ -264,3 +266,14 @@ def test_iteration(self):
 
     def test_choices_len(self):
         self.assertEqual(len(StringTestClass), 4)
+
+    def test_order_annotation(self):
+        case = OrderedChoices.get_order_expression('dummy')
+
+        expected = Case(
+            When(dummy='b', then=Value(0)),
+            When(dummy='a', then=Value(1)),
+            output_field=IntegerField()
+        )
+
+        self.assertEqual(repr(case), repr(expected))

docs/choices.rst

@@ -230,3 +230,31 @@ Returns the actual ``ChoiceItem`` instance for a given value:
     <ChoiceItem value=2 label='label 2' order=1>
 
 This allows you to inspect any ``ChoiceItem`` attributes.
+
+get_order_expression
+++++++++++++++++++++
+
+Build the ``Case``/``When`` statement to use in queryset annotations.
+
+Choices defined get an implicit or explicit order, which can have semantic
+value. This ORM expression allows you to map choice values to the order value,
+as an integer, on the database level.
+
+It is then available for subsequent filtering, allowing more work to be done
+in the database instead of in Python.
+
+.. code-block:: python
+
+    >>> class MyChoices(DjangoChoices):
+    ...     first = ChoiceItem('first')
+    ...     second = ChoiceItem('second')
+
+    >>> order = MyChoices.get_order_expression('some_field')
+    >>> queryset = Model.objects.annotate(some_field_order=order)
+    >>> for item in queryset:
+    ...     print(item.some_field)
+    ...     print(item.some_field_order)
+    # first_
+    # 1
+    # second
+    # 2

runtests.py

@@ -1,15 +1,15 @@
-try:
-    import unittest2 as unittest
-except ImportError:
-    import unittest
-
+import unittest
 from os import path
 from sys import stdout
 
+from django.conf import settings
+
 
 def get_suite():
     disc_folder = path.abspath(path.dirname(__file__))
 
+    settings.configure(SECRET_KEY='dummy')
+
     stdout.write("Discovering tests in '%s'..." % disc_folder)
     suite = unittest.TestSuite()
     loader = unittest.loader.defaultTestLoader

setup.py

@@ -11,7 +11,7 @@
     license="MIT",
     description="Sanity for the django choices functionality.",
     long_description=readme,
-    install_requires=['Django>=1.8'],
+    install_requires=['Django>=1.11'],
     test_suite='runtests.get_suite',
     url="https://github.com/bigjason/django-choices",
     author="Jason Webb",
@@ -24,14 +24,11 @@
         "License :: OSI Approved :: MIT License",
         "Intended Audience :: Developers",
         "Framework :: Django",
-        "Framework :: Django :: 1.8",
-        "Framework :: Django :: 1.9",
-        "Framework :: Django :: 1.10",
         "Framework :: Django :: 1.11",
         "Framework :: Django :: 2.0",
         "Framework :: Django :: 2.1",
+        "Framework :: Django :: 2.2",
         "Programming Language :: Python :: 2.7",
-        "Programming Language :: Python :: 3.3",
         "Programming Language :: Python :: 3.4",
         "Programming Language :: Python :: 3.5",
         "Programming Language :: Python :: 3.6",

tox.ini

@@ -1,30 +1,25 @@
 [tox]
 envlist =
-  py33-django18,
-  py{27,34,35,py}-django{18,19,110,111},
-  py34-django20,
-  py{35,36,37}-django{20,21}
+  py{27,34,35,36,37,py}-django111,
+  py{34,35,36,37}-django20,
+  py{35,36,37}-django{21,22},
   docs,
   isort
 skip_missing_interpreters = true
 
 [travis:env]
-DJANGO = 
-  1.8: django18
-  1.9: django19
-  1.10: django110
+DJANGO =
   1.11: django111
   2.0: django20
   2.1: django21
+  2.2: django22
 
 [testenv]
 deps=
-  django18: Django>=1.8,<1.9
-  django19: Django>=1.9,<1.10
-  django110: Django>=1.10,<1.11
   django111: Django>=1.11,<2.0
   django20: Django>=2.0,<2.1
   django21: Django>=2.1,<2.2
+  django22: Django>=2.2,<3.0
   coverage
   coveralls
 commands=coverage run --rcfile={toxinidir}/.coveragerc {toxinidir}/setup.py test