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Drop in replacement for django's many to many field with sorted relations.

Project description

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.

sortedm2m requires at least django 1.2. Django 1.1 or earlier is not supported.

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)

Admin

There is a small caveat with using the sorted m2m relation in django’s admin. Because django renderes many to many relations in a select list by default its not possible for the SortedManyToManyField to determine the desired ordering.

So you have to work around this to use the sorting on models managed by the admin. You can tell the admin to display a simple input box instead of the select list where you can then enter raw ids seperated by commas. If you use that widget you can specify the ordering by changing the order of the ids in the input box.

Use the raw_id_fields option in the ModelAdmin definition for you model. Example:

from django.contrib import admin

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

Project details


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