+
+ @classmethod
+ def get_by_location(cls, user, location, create=False):
+ Book = apps.get_model('catalogue', 'Book')
+ try:
+ slug, anchor = location.split('/')
+ except:
+ return None
+ instance = cls.objects.filter(
+ user=user,
+ book__slug=slug,
+ anchor=anchor
+ ).first()
+ if instance is None and create:
+ try:
+ book = Book.objects.get(slug=slug)
+ except Book.DoesNotExist:
+ return None
+ instance = cls.objects.create(
+ user=user,
+ book=book,
+ anchor=anchor
+ )
+ return instance