Question

我的播放列表里面有很多歌曲，当我从查询集中获取歌曲时，我希望这些歌曲保持整齐。我尝试过这个显而易见的事情 - 一个＆＃39;通过＆＃39;使用order_by =＆＃39; song_order＆＃39; - 但是这不会起作用，并试图让它在Song上使用代理模型（参见下面的代码）最终会抛出这个错误：

AttributeError: 'ManyToManyField' object has no attribute '_m2m_reverse_name_cache'

目前，这就是它的样子：

class Song(models.Model):
    sid = models.AutoField(primary_key=True)
    id = models.CharField(max_length=60)
    title = models.CharField(max_length=300)
    artist_name = models.CharField(max_length=250)
    artist_id = models.CharField(max_length=50)
    mood = models.ForeignKey('Mood', related_name='songs_with_mood', blank=True, null=True)

    def __unicode__ (self):
        return "%s - %s" % (self.title, self.id)


class PlaylistSong(Song):
    class Meta:
        proxy = True
        ordering = ['playlist_song_ordering__song_order']
         # ^ this is the line responsible for the Attribute Error

class PlaylistSongs(models.Model):
    song = models.ForeignKey("PlaylistSong", related_name='playlist_song_ordering')
    playlist = models.ForeignKey("Playlist")
    song_order = models.IntegerField()

    class Meta:
        db_table = "api_playlist_songs"
        ordering = ['song_order']

class Playlist(models.Model):
    owner = models.ForeignKey('UserProfile', related_name='owned_playlists')
    title = models.CharField(max_length=70)
    songs = models.ManyToManyField('Song', related_name='in_playlists', through='PlaylistSongs')
    created = models.DateTimeField(auto_now_add=True)

    class Meta:
        ordering = ('-created',)
        unique_together = ("owner", "title", "created",)

如何在Django中订购ManyToManyField并将它们按顺序排除？

0 个答案: