Hello,
Let say I want to enforce a database constraint saying a "book's author age
is over 18".
As you may guess, books and authors are each described with a Model
subclass with a foreign key (in this example each book is written by a
single author) linking both.
class Author(models.Model):
age = models.SmallIntegerField()
class Book(models.Model):
author = models.ForeignKey(Author, on_delete=models.PROTECT)
class Meta:
constraints = [
models.CheckConstraint(check=models.Q(<WHATEVER>__gt=18),
name='age_check'),
]
I've tried replacing <WHATEVER> above with author_age or author__age.
In both cases, makemigrations works but migrate fails with:
django.core.exceptions.FieldError: Joined field references are not
permitted in this query
Can I work around this ?
Any working example ?
Best regards
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