Django Admin Many To Many Subset

I'm trying to integrate in Django admin the next three related models: # models.py class Seminar(models.Model): title = models.CharField(max_length=128, unique=True) start_

Solution 1:

Well so, just before asking here, I did something similar to Django's auth.User model by using different forms for add/change views. I hoped there was a better solution, obviously not.

So here is what I did:

# models.pyclassRegistration(models.Model):
    # [...] - add form excludes it, should allow blank on events field
    events = models.ManyToManyField('Event', blank=True, null=True)


# admin.pyclassRegistrationAdmin(admin.ModelAdmin):
    change_form = RegistrationChangeForm

    defget_form(self, request, obj=None, **kwargs):
        defaults = {}
        if obj isNone:
            defaults.update(exclude=('events',))
        else:
            defaults.update(form=self.change_form)
        defaults.update(kwargs)
        returnsuper(RegistrationAdmin, self).get_form(request, obj, **defaults)


# forms.pyclassRegistrationChangeForm(forms.ModelForm):
    classMeta:
        model = Registration
        exclude = ('seminar',)

    def__init__(self, *args, **kwargs):
        super(RegistrationChangeForm, self).__init__(*args, **kwargs)
        self.fields['events'].choices = Event.objects.filter(seminar=kwargs.get('instance').seminar).values_list('pk','title')

So, when adding we simply ignore events (registration is saved with nulled events) and then, on change a list of events can be selected based on the previously defined seminar which is then ignored (since we can't reload the related events list).