Django 3 Web Development Cookbook - Fourth Edition

How to do it...

Set the database constraints in the Meta class of the Idea model as follows:

# myproject/apps/ideas/models.pyfrom django.db import modelsfrom django.utils.translation import gettext_lazy as _class Idea(models.Model):    author = models.ForeignKey(        settings.AUTH_USER_MODEL,        verbose_name=_("Author"),        on_delete=models.SET_NULL,        blank=True,        null=True,        related_name="authored_ideas",    )    title = models.CharField(        _("Title"),        max_length=200,    )    class Meta:        verbose_name = _("Idea")        verbose_name_plural = _("Ideas")        constraints = [            models.UniqueConstraint(                fields=["title"],                condition=~models.Q(author=None),                name="unique_titles_for_each_author",            ),            models.CheckConstraint(                check=models.Q(                    title__iregex=r"^\S.*\S$" # starts with non-whitespace, ...