How to validate CHOICES for objects.create() method?

Question

I have the following model:

from django.db import models


class Artist(models.Model):

    TYPE_CHOICES = (
        ('Person', 'Person'),
        ('Group', 'Group'),
        ('Other', 'Other'),)

    name = models.CharField(max_length=100)
    type = models.CharField(max_length=20, choices=TYPE_CHOICES)

The problem is that if I create an object like this: Artist.objects.create(...) the type validation doesn't work. How can I activate the validation for this?

Normally it does not even check this when you construct an object like `a = Artist()` and then `artist.save()` it. This is done in the `artist.clean()` function, and this is normally only called in forms, etc. — Willem Van Onsem, Oct 27 '18 at 20:02
I've just added super().clean() in the save method but it doesn't work. — Nepo Znat, Oct 27 '18 at 20:10
But you then should call `self.clean()`, since now you look for the *previous* clean method. You also need to call `self.clean_fields()`, and `self.validate_unique()`. — Willem Van Onsem, Oct 27 '18 at 20:14
Ah great thanks, that's working. I wonder why Django doesn't do this by default. — Nepo Znat, Oct 27 '18 at 20:17
If I recall correctly, due to performance reasons. Note that `bulk_create`, and `SomeModel.objects.all().update(..)`, etc. can still surpass this (since some ORM calls circumvent `.save()`). — Willem Van Onsem, Oct 27 '18 at 20:18

score 2 · Accepted Answer · answered Oct 27 '18 at 20:19

You can make an (abstract) model that first performs validations before saving the object with:

class ValidatedModel(models.Model):

    class Meta:
        abstract = True

    def save(self, *args, **kwargs):
        self.clean_fields()      # validate individual fields
        self.clean()             # validate constraints between fields
        self.validate_unique()   # validate uniqness of fields
        return super(ValidatedModel, self).save(*args, **kwargs)

and then for example use this in models like:

class Artist(ValidatedModel):

    TYPE_CHOICES = (
        ('Person', 'Person'),
        ('Group', 'Group'),
        ('Other', 'Other'),)

    name = models.CharField(max_length=100)
    type = models.CharField(max_length=20, choices=TYPE_CHOICES)

Note that the above will validate model object in case you call the .save() method (or some other function does that), but some methods circumvent calling the .save() method like Model.objects.bulk_create(..), etc.

How to validate CHOICES for objects.create() method?

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