Django models.py 循环外键
我有一个 django 应用程序,它基本上只是一个相册.现在我有两个模型:Image
和 Album
.除其他外,每个 Album
都有一个指向 Image
的外键作为其缩略图,每个 Image
都有一个指向 的外键它所属的专辑
.但是,当我尝试使用 manage.py syncdb
或 manage.py sqlall
时,我收到错误提示该类未在模型中首先定义.py 在定义的第一个类中使用时未定义.
I have a django app which basically is just a photo album. Right now I have two models: Image
and Album
. Among other things, each Album
has a foreign key to an Image
to be its thumbnail and each Image
has a foreign key to the Album
it belongs in. However, when I try to use manage.py syncdb
or manage.py sqlall
I get errors saying the class not defined first in models.py isn't defined when it is used in the first class defined.
models.py(删节):
models.py (abridged):
from django.db import models
import os
class Album(models.Model):
thumb = models.ForeignKey(Image, null=True, blank=True)
class Image(models.Model):
image = models.ImageField(upload_to='t_pics/images')
thumb = models.ImageField(upload_to='t_pics/images/thumbs')
album = models.ForeignKey(Album)
执行 manage.py sqlall appname
时出现错误:
[...]
File "/path/to/file/appname/models.py", line 4, in ?
class Album(models.Model):
File "/path/to/file/appname/models.py", line 5, in Album
thumb = models.ForeignKey(Image, null=True, blank=True)
NameError: name 'Image' is not defined
当我在 models.py 中切换类的顺序时,我得到了同样的错误,除了它说 'Album' undefined
而不是 'Image' undefined
我也试过在第一堂课中评论依赖关系,然后在其他所有内容成功导入后取消评论,但这没有帮助.我应该如何去做这项工作?我不愿意制作整个第三类 Thumb
因为它会有很多与 Image
相同的代码我也很确定我可以手动添加外键到数据库,但我希望它是干净的而不是hackish.
I get the same error when I switch the order of the classes in models.py except it says 'Album' undefined
instead of 'Image' undefined
I also tried commenting the dependancy in the first class then uncommenting after everything else was successfully imported but that didn't help. How should I go about making this work? I'm reluctant to make an entire third class Thumb
because it will have a lot of the same code as Image
I'm also pretty sure I could manually add the foreign key to the database but I want this to be clean and not hackish.
推荐答案
你实际上没有循环引用;问题是,在您定义专辑时,您还没有定义图像.你可以改用字符串来解决这个问题:
You don't actually have a circular reference; the issue is that, at the time you define Album, you haven't defined Image yet. You can fix that by using a string instead:
class Album(models.model):
thumb = models.ForeignKey('Image', null=True, blank=True)
但是,在这种情况下,您可能希望使用 OneToOneField 而不是外键.(请注意,您仍然必须对字符串使用该技巧).
However, in this case, you might want to use a OneToOneField instead of a foreign key. (Note that you'll still have to use the trick with the string, though).
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