[英]Django: get related set from a related set of a model
class Book(models.Model):
# fields
class Chapter(models.Model):
book = models.ForeignKey(Book)
class Page(models.Model):
chapter = models.ForeignKey(Chapter)
I want all the pages of the book A, possibly without cycling every chapter to fetch the pages. 我想要书A的所有页面,可能没有骑自行每一章来获取页面。
book = Book.objects.get(pk=1)
pages = book.chapter_set.page_set #?!?
You can't do it that way. 你不能这样做。 chapter_set is a query set, it doesn't have an attribute page_set.
chapter_set是一个查询集,它没有属性page_set。
Instead, turn it around: 相反,转过来:
Page.objects.filter(chapter__book=my_book)
When you query cross models, double underscores may help 查询交叉模型时,双下划线可能会有所帮助
book = Book.objects.get(pk=1)
pages = Page.objects.filter(chapter__book=book)
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