外键访问

问题描述

-------------------------------------------- MODELS.PY --------------------------------------------

--------------------------------------------MODELS.PY--------------------------------------------

class Artist(models.Model):
    name = models.CharField("artist", max_length=50) #will display "artist" in front of artist-name
    year_formed = models.PositiveIntegerField()

#   Initialization Example
#     newArtist = Artist(name = 'Artist Name', year_formed = 2015);
#     newArtist.save();




# Album will be a foreign key
# Many to 1 relation ie (Single artist -> many albums)
class Album(models.Model):
    name = models.CharField("album", max_length=50) #will display "album" in front of album-name
    artist = models.ForeignKey(Artist)

--------------------- -------- SHELL --------------------------------

-----------------------------SHELL--------------------------------

newArtist = Artist(name = 'GBA',year_formed = 1990)
newArtist.save()
album1 = Album(name = 'a',artist = newArtist)
album2 = Album(name = 'b',artist = newArtist)
album3 = Album(name = 'c',artist = newArtist)
album1.save()
album2.save()
album3.save()
allAlbums = Album.objects.all()

for e in allAlbums:
    print(e.artist.name)

-------------- ------＃结果错误-------------------------

--------------------#Results in error-------------------------

 Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/django/db/models/fields/related_descriptors.py", line 170, in __get__
    rel_obj = getattr(instance, self.cache_name)
AttributeError: 'Album' object has no attribute '_artist_cache'
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "<input>", line 2, in <module>
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/django/db/models/fields/related_descriptors.py", line 179, in __get__
    rel_obj = qs.get()
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/django/db/models/query.py", line 385, in get
    self.model._meta.object_name
DB_start.models.DoesNotExist: Artist matching query does not exist.

我遵循正确的语法作为文档，但导致错误。如何成功访问外键字段？尝试打印（e__name）。

I am following the correct syntax as documentation yet results in error. How can I successfully access the foreign key fields? Have tried print (e__name) as well.

推荐答案

您的问题来自于您设置的密钥的位置。 p>

Your problem comes from the placement of the key you have set up.

class Artist():
    blah = models.TextField()


class Album()
    blah = models.ForeignKey(blah)

这是数据库将工作

-Cheers

52行

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