sortedm2m is a drop-in replacement for django's own
SortedManyToManyField behaves like the original one but
remembers the order of added relations.
Imagine that you have a gallery model and a photo model. Usually you want a relation between these models so you can add multiple photos to one gallery but also want to be able to have the same photo on many galleries.
This is where you usually can use many to many relation. The downside is that django's default implementation doesn't provide a way to order the photos in the gallery. So you only have a random ordering which is not suitable in most cases.
You can work around this limitation by using the
provided by this package as drop in replacement for django's
ManyToManyField in your models:
from django.db import models from sortedm2m.fields import SortedManyToManyField class Photo(models.Model): name = models.CharField(max_length=50) image = models.ImageField(upload_to='...') class Gallery(models.Model): name = models.CharField(max_length=50) photos = SortedManyToManyField(Photo)
If you use the relation in your code like the following, it will remember the order in which you have added photos to the gallery.
gallery = Gallery.objects.create(name='Photos ordered by name') for photo in Photo.objects.order_by('name'): gallery.photos.add(photo)
You can use the following arguments to modify the default behavior:
You can set the
False which will force the
SortedManyToManyField in behaving like Django's original
ManyToManyField. No ordering will be performed on relation nor will the
intermediate table have a database field for storing ordering information.
Specifies how the field is called in the intermediate database table by which the relationship is ordered. You can change its name if you have a legacy database that you need to integrate into your application.
ManyToManyField to be a
If you are using Django's migration framework and want to change a
ManyToManyField to be a
SortedManyToManyField (or the other way
around), you will find that a migration created by Django's
will not work as expected.
In order to migrate a
ManyToManyField to a
change the field in your models to be a
appropriate and create a new migration with
Before applying it, edit the migration file and change in the
AlterSortedManyToManyField (import it
sortedm2m.operations). This operation will take care of changing the
intermediate tables, add the ordering field and fill in default values.
SortedManyToManyField provides a custom widget which can be used to sort
the selected items. It renders a list of checkboxes that can be sorted by
To use the widget in the admin you need to add
sortedm2m to your
INSTALLED_APPS settings, like:
INSTALLED_APPS = ( 'django.contrib.auth', 'django.contrib.contenttypes', 'django.contrib.sessions', 'django.contrib.sites', 'django.contrib.messages', 'django.contrib.staticfiles', 'django.contrib.admin', 'sortedm2m', '...', )
Otherwise it will not find the css and js files needed to sort by drag'n'drop.
Finally, make sure not to have the model listed in any
filter_vertical tuples inside of your
If you did it right, you'll wind up with something like this:
It's also possible to use the
SortedManyToManyField with admin's
raw_id_fields option in the
ModelAdmin definition. Add the name of the
SortedManyToManyField to this list to get a simple text input field. The
order in which the ids are entered into the input box is used to sort the
items of the sorted m2m relation.
from django.contrib import admin class GalleryAdmin(admin.ModelAdmin): raw_id_fields = ('photos',)
You can find the latest development version on github. Get there and fork it, file bugs or send me nice wishes.
Running the tests
I recommend to use
tox to run the tests for all relevant python versions
all at once. Therefore install
pip install tox, then type in
the root directory of the
However using tox will not include the tests that run against a PostgreSQL
database. The project therefore contains a
Vagrantfile that uses vagrant
to setup a virtual machine including a working PostgreSQL installation. To
run the postgres tests, please install vagrant and then run:
This will bring up and provision the virtual machine and runs the testsuite against a PostgreSQL database.