Django Change all other Boolean fields except one-CodePudding

I have a model which has a boolean field:

class Library(SocialLinksModelMixin):
    """
    Represents book shelves and places where people have / leave books.
    """
    user = models.ForeignKey(...)
    is_main = models.BooleanField(default=False)

User can have multiple Libraries and I would like to allow setting the main one to ease the flow in the app.

What is the easiest way for switching only one Library is_main to True and all others to False (There is always only 1 Library for a user that is main)

I'm thinking about querying for all libraries and updating each and every one. Maybe there is another way to do that functionality?

CodePudding user response：

If you have the primary key of the Library to set the is_main to True, you can work with:

from django.db.models import Q

Library.objects.filter(user=my_user).update(
    is_main=Q(pk=my_pk)
)

You might also want to enforce at database level that there can only be one Library with is_main=True per user:

from django.conf import settings
from django.db.models import Q

class Library(SocialLinksModelMixin):
    """
    Represents book shelves and places where people have / leave books.
    """
    user = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE
    )
    is_main = models.BooleanField(default=False)
    
    class Meta:
        constraints = [
            models.UniqueConstraint(fields=('user',), condition=Q(is_main=True), name='one_main_per_user')
        ]