Limiting choices in a lookup by exclusion

[Gordon R. Burgess]

I have this code, and with Django 1.10 it works as expected:

class Location(models.Model):

    name = models.CharField(max_length = 32, unique = True)

    street = models.CharField(max_length = 32)

    detail = models.CharField(max_length = 32, blank = True, null = True)

    city = models.CharField(max_length = 32)

    state = USStateField()

    zip = USZipCodeField()

    phone = models.ManyToManyField(Phone, limit_choices_to = {'type_id':'H'})

but what I'd like to do is restrict the choices of phone numbers for Locations to those that aren't 'C' (cell phones) - I've found some hints, but they're all for older versions of Django - it seems like:

    phone = models.ManyToManyField(Phone, limit_choices_to = {'type_id__ne':'C'})

ought to work - but this provokes a TypeError:

Related Field got invalid lookup: ne

Thanks!

[C. Kirby]

django doesn't have an ne operator in the orm. You want to use a negated Q object for your limit_choices_to. try:

from django.db.models import Q

phone = models.ManyToManyField(Phone, limit_choices_to = ~Q(type_id = 'C'))

[Melvyn Sopacua]

And there's 2 other options to consider:

 

• The ne lookup is actually the first example in the documentation for custom lookups. So you get its implementation for free and can consider adding it.
• You can extend Field to add exclude_choices() which sets limit_choices_to to the negation of the argument as below - so wrap it with ~Q().

All depending on how isolated your case is in the project/app.

--

Melvyn Sopacua