Django ManyToMany all values by default

Question

I have the following model:

class Product(models.Model):
    provinces = models.ManyToManyField('Province', related_name='formats')

By default, products can be sold in every province. How can I define the model "Product" so that every product created has all provinces by default?

Thanks!

This could do the job: [post_save](https://docs.djangoproject.com/en/1.8/ref/signals/#post-save) — Gocht, Jul 24 '15 at 19:12

score 7 · Answer 1 · answered Jul 24 '15 at 19:33

7

Use the default key. You can't directly set default model values to an iterable like a list, so wrap them in a callable, as the Django documentation advises: https://docs.djangoproject.com/en/1.8/ref/models/fields/

def allProvinces():
    return provincesList

provinces = models.ManyToManyField('Province', related_name='formats', default=allProvinces)

answered Jul 24 '15 at 19:33

Sam Holladay

113
1
7

I know this is old, but I stumbled onto this answer first and eventually [this (old and "unresolved") ticket](https://code.djangoproject.com/ticket/2750). I personally had to use the post_save signal suggered by @Gocht – tgrandje Sep 16 '20 at 12:03

score 4 · Answer 2 · answered Dec 01 '20 at 15:05

4

You need to use post_save signal.

You can not use default field option for many-to-may fields as mentioned here

answered Dec 01 '20 at 15:05

Ömer Mert Ekşioğlu

71
7

score 1 · Answer 3 · answered Jan 14 '21 at 09:52

1

You cannot directly add a list to M2M directly, you should first get the objects :

def allProvinces():
    provinceList = Province.objects.all()
    return provinceList

And then add the default=allProvinces :)

answered Jan 14 '21 at 09:52

MrAch26

13
3

score 1 · Answer 4 · answered Nov 16 '22 at 16:36

Expanding from https://stackoverflow.com/a/32068983/1581629 I did this:

class Product(models.Model):
    ...
    def save(self, *args, **kwargs):
        created_flag = False
        if not self.pk:
            created_flag = True
        super().save(*args, **kwargs)
        if created_flag:
            self.provinces = Province.objects.all()

Django ManyToMany all values by default

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