Prefetch with to attr #djangotip02

shell.py

# $ python app/manage.py shell

from products.models import Category
from django.db.models import Prefetch

# Get the first category with subcategories
category = Category.objects.filter(subcategories__isnull=False).first()

# Try to access the `active_subcategories` attribute
category.active_subcategories

# Now let’s load our object with the new Prefetch
category = Category.objects.filter(
    subcategories__isnull=False
).prefetch_related(
  Prefetch(
    'subcategories',
    queryset=Category.objects.filter(is_active=True),
    to_attr='active_subcategories'
)).first()

# Try to access the `active_subcategories` attribute
category.active_subcategories