Django: "Cannot assign must be a "X" instance", don't want to fetch the object

I have the following view on my Django app and I need to update one object

status_id is a ForeignKey field and it has some default values loaded via fixtures

def stopObject(request, id_object):
    object = Object.objects.get(id=id_object)
    object.status_id = 1
    object.save()

I’m getting the classical error where I need to assign the object, not its Id. There are countless questions on SO about this problem, but I came looking for an answer I didn’t found

I know very well I can just perform a fetch from the database and assign to status, but I want to explore other possibilities, even though they may not be the best practices

EDIT sharing the models:

class Status(models.Model):
    id = models.AutoField(primary_key=True)
    description = models.CharField(max_length=32, unique=True)

class Object(models.Model):
    id = models.AutoField(primary_key=True)
    status_id = models.ForeignKey(Status,
                                  db_column="status_id",
                                  default=3,
                                  null=True,
                                  blank=True,
                                  related_name='objects',
                                  on_delete=models.SET_NULL)
    # other fields

>Solution :

status_id is a ForeignKey.

Normally one does not add a suffix …_id to a ForeignKey field, since Django will automatically add a "twin" field with an …_id suffix. Therefore it should be status, instead of status_id, so:

class Object(models.Model):
    status = models.ForeignKey(
        Status,
        default=3,
        null=True,
        blank=True,
        related_name='objects',
        on_delete=models.SET_NULL,
    )

this then also prevents having to specify the db_column='status_id'.

If you thus rename the field to status, you can use status_id. If not, you can use:

# if the field is named status
def stopObject(request, id_object):
    object = Object.objects.get(id=id_object)
    object.status_id = 1
    object.save()

If you decide to keep it status_id for some reason, we can use:

# if the field is remains status_id
def stopObject(request, id_object):
    object = Object.objects.get(id=id_object)
    object.status_id_id = 1
    object.save()

You can boost performance further by just updating the Object instead of fetching and saving:

# if the field is remains status_id
def stopObject(request, id_object):
    object = Object.objects.filter(id=id_object).update(status_id_id=1)

or with the renamed field:

# if the field is named status
def stopObject(request, id_object):
    object = Object.objects.filter(id=id_object).update(status_id=1)

Note: Django will add by default an AutoField ^[Django-doc] as primary_key=True to a model with name id if you do not specify a primary key yourself, so there is no need to explicitly declare a primary key.