def test_wrong_prefetch_subclass_and_instance(self):
with self.assertRaises(InvalidPrefetch) as cm:
PrefetchManager(latest_book_as_instance=LatestBook(), )
self.assertEqual(cm.exception.args, (
"Invalid prefetch definition latest_book_as_instance. This prefetcher needs to be a class not an "
"instance.", ))
class BookNote(models.Model):
book = models.ForeignKey("Book", models.CASCADE, null=True)
bogus = models.ForeignKey("Book",
models.CASCADE,
null=True,
related_name="+")
notes = models.TextField()
objects = PrefetchManager()
class Book(models.Model):
class Meta:
get_latest_by = 'created'
name = models.CharField(max_length=100)
created = models.DateTimeField(auto_now_add=True)
author = models.ForeignKey(Author)
publisher = models.ForeignKey(Publisher, null=True)
if VERSION < (1, 2):
tags = models.ManyToManyField(Tag, through="Book_Tag")
else:
tags = models.ManyToManyField(Tag)
objects = PrefetchManager(
tags = Prefetcher(
filter = lambda ids: (Book_Tag if VERSION < (1, 2) else Book.tags.through).objects.filter(book__in=ids),
reverse_mapper = lambda book_tag: [book_tag.book_id],
decorator = lambda user, book_tags=():
setattr(user, 'prefetched_tags', [i.tag for i in book_tags])
),
similar_books = Prefetcher(
filter = lambda ids: Book.objects.filter(author__in=ids),
mapper = lambda book: book.author_id,
reverse_mapper = lambda book: [book.author_id],
decorator = lambda book, books=():
setattr(book.author, 'prefetched_books', books),
collect = True,
),
similar_books_missing_collect = Prefetcher(
filter = lambda ids: Book.objects.filter(author__in=ids),
mapper = lambda book: book.author_id,
reverse_mapper = lambda book: [book.author_id],
decorator = lambda book, books=():
setattr(book.author, 'prefetched_books', books),
),
)
@property
def similar_books(self):
if hasattr(self.author, 'prefetched_books'):
return [i for i in self.author.prefetched_books if i != self]
else:
return Book.objects.filter(
author = self.author_id
).exclude(
id = self.id
)
@property
def selected_tags(self):
if hasattr(self, 'prefetched_tags'):
return self.prefetched_tags
else:
return self.tags.all()
class Author(models.Model):
name = models.CharField(max_length=100)
objects = PrefetchManager(
books = Prefetcher(
filter = lambda ids: Book.objects.filter(author__in=ids),
mapper = lambda author: author.id,
reverse_mapper = lambda book: [book.author_id],
decorator = lambda author, books=():
setattr(author, 'prefetched_books', books)
),
latest_n_books = LatestNBooks,
latest_book_as_class = LatestBook,
latest_book = Prefetcher(
filter = lambda ids: Book.objects.filter(author__in=ids),
reverse_mapper = lambda book: [book.author_id],
decorator = lambda author, books=(): setattr(
author,
'prefetched_latest_book',
max(books, key=lambda book: book.created) if books else None
)
),
silly = SillyPrefetcher,
)
@property
def books(self):
if hasattr(self, 'prefetched_books'):
return self.prefetched_books
else:
return self.book_set.all()
@property
def latest_book(self):
if hasattr(self, 'prefetched_latest_book'):
return self.prefetched_latest_book
else:
try:
return self.book_set.latest()
except Book.DoesNotExist:
return
class BookNote(models.Model):
book = models.ForeignKey("Book", null=True)
notes = models.TextField()
objects = PrefetchManager()