是否可以从 django 模型进行查询?
我有 2 个模型:
class Book(models.Model):
...
def copies_available(self):
pass
和
class BookCopy(models.Model):
...
book_category = models.ForeignKey(Book, related_name='copies')
issued_to = models.ForeignKey(EndUser, related_name='issued_books', null=True, blank=True)
我想copies_available()
返回它的BookCopy
实例数Book
issued_to
None