小编Tia*_*imo的帖子

我已经在trunk中尝试了django 1.4中的prefetch_related(),并且无法使其预取反向查找.

我的简化模型(每本书都有很多价格):

class Book(models.Model):
    # some fields

class Price(models.Model):
    book = models.ForeignKey(Book)

我的观点是:

books = Book.objects.prefetch_related('price')

然后,我收到了AttributeError消息:

AttributeError: Cannot find 'price' on Book object, 'price' is an invalid parameter to prefetch_related()

如何使它工作？谢谢.

可以在此处找到问题:http:
//code.google.com/codejam/contest/dashboard？c = 975485#s = p3

我不明白为什么
answer = no. of elements that are not in the correct position

例如,假设我必须对此数组进行排序:

3 1 2

所以我这样想:

Array: 3 1 2  
1st: freeze 2 to sort 1 (take 2 hits)  
Array: 1 3 2  
2nd: freeze 1 to sort 2 and 3 (take another 2 hits)

因此,我的回答是4,但正确答案是3.
有人能澄清这个问题吗？