django-sortedm2m

sortedm2m is a drop-in replacement for django's own ManyToManyField. The provided SortedManyToManyField behaves like the original one but remembers the order of added relations.

Usecases

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 SortedManyToManyField provided by this package as drop in replacement for django's ManyToManyField.

Usage

Use SortedManyToManyField like 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)

`SortedManyToManyField`

You can use the following arguments to modify the default behavior:

`sorted`

Default: True

You can set the sorted to 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.

`sort_value_field_name`

Default: 'sort_value'

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.

Admin

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 drag'n'drop.

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.

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.

Example:

from django.contrib import admin

class GalleryAdmin(admin.ModelAdmin):
    raw_id_fields = ('photos',)

Contribute

You can find the latest development version on github. Get there and fork it, file bugs or send me nice wishes.

Feel free to drop me a message about critique or feature requests. You can get in touch with me by mail or twitter.

blturner/django-sortedm2m