python – Django – 从实例访问模型的“直通”表中的字段
作者:互联网
我与通过表有多对多的关系,如下所示:
class Chapter(models.Model):
name = models.CharField(max_length=255,)
slides = models.ManyToManyField('Slide', blank=True, related_name='chapters', through='SlideOrder')
# ...
class Slide(models.Model):
title = models.CharField(max_length=255,)
# ...
class SlideOrder(models.Model):
chapter = models.ForeignKey(Chapter)
slide = models.ForeignKey(Slide)
number = models.PositiveIntegerField()
我可以按顺序获取章节的幻灯片:
chapter = Chapter.objects.get(pk=1)
chapter_slides = chapter.slides.order_by('slideorder')
但是,在处理单个幻灯片实例时,我无法访问幻灯片顺序:
slide = Slide.objects.get(pk=1)
如果我在幻灯片实例上执行以下操作,则可以看到所有可能的字段:
print slide._meta.get_all_field_names()
['title', u'chapters', 'slideorder', u'id']
但是,尝试访问slideorder字段给出了以下内容:
slide.slideorder
Traceback (most recent call last):
File "<console>", line 1, in <module>
AttributeError: 'Slide' object has no attribute 'slideorder'
我可以访问除slideorder之外列出的所有属性.如何访问幻灯片的订单?
解决方法:
您可以直接过滤SlideOrder模型
slide = Slide.objects.get(pk=1)
slide_orders = SlideOrder.objects.filter(slide=slide)
for slide_order in slide_orders:
print slide_order.number
或者向后关注外键:
slide = Slide.objects.get(pk=1)
slide_orders = slide.slideorder_set.all()
for slide_order in slide_orders:
print slide_order.number
有关详细信息,请参阅extra fields on many-to-many relationships上的文档.
标签:python,django,many-to-many 来源: https://codeday.me/bug/20191002/1845138.html