Django REST Framework，通过直通表订购m2m序列化

Question

我正在尝试使用Django REST Framework（3.3.1）生成JSON，它应使用直通模型对m2m字段进行排序。这适用于普通的django视图 - 订单受到尊重（即在管理列表中）。但是，使用标准DRF的ModelSerializers集合，django模型上指定的直通表不用于返回的m2m集的排序。

有没有一种简单的方法来实现我追求的顺序？或者我是否需要生成数据并返回我自己的DRF响应？

我有以下型号：

class Pitch(models.Model):
    """ A pitch like 'A4" (A at octave 4) with midi note - ie 60 = middle C (C3) """
    name = models.CharField(max_length=5)
    midi_note = models.IntegerField()

    def __unicode__(self):
        return self.name

    class Meta:
        ordering = ['midi_note']
        verbose_name_plural = 'pitches'


class Pattern(models.Model):
    """ ie A Major """
    name = models.CharField(max_length=50, default="")
    pitches = models.ManyToManyField(Pitch, through='PitchPosition')

    def __unicode__(self):
        return u"{0}".format(self.name)


class PitchPosition(models.Model):
    """
    The through table for a pitch in a pattern, needed as 
    scales/arpeggios go up and down, so pitches appear 
    twice in the list

    """
    pattern = models.ForeignKey(Pattern)
    pitch = models.ForeignKey(Pitch)
    order = models.IntegerField(default=0)

    def __unicode__(self):
        return u"{0} ({1})".format(self.pitch, self.pattern)

    class Meta:
        ordering = ['pattern', 'order']

使用DRF序列化数据，直通表排序未得到遵守：

class PitchSerializer(serializers.ModelSerializer):
    class Meta:
        model = Pitch
        fields = ('name', 'midi_note')


class PatternSerializer(serializers.ModelSerializer):
    name = serializers.CharField()
    pitches = PitchSerializer(many=True)

    class Meta:
        model = Pattern
        fields = ('name', 'pitches')

产地：

[
    {
        "name": "D Major",
        "pitches": [
            {
                "name": "D4",
                "midi_note": 62
            },
            {
                "name": "D4",
                "midi_note": 62
            },
            {
                "name": "E4",
                "midi_note": 64
            },
            {
                "name": "E4",
                "midi_note": 64
            },
            {
                "name": "F#4",
                "midi_note": 66
            },
            {
                "name": "F#4",
                "midi_note": 66
            },
            {
                "name": "G4",
                "midi_note": 67
            },
            {
                "name": "G4",
                "midi_note": 67
            },
            {
                "name": "A4",
                "midi_note": 69
            },
            {
                "name": "A4",
                "midi_note": 69
            },
            {
                "name": "B4",
                "midi_note": 71
            },
            {
                "name": "B4",
                "midi_note": 71
            },
            {
                "name": "C#5",
                "midi_note": 73
            },
            {
                "name": "C#5",
                "midi_note": 73
            },
            {
                "name": "D5",
                "midi_note": 74
            }
        ]
    }
]

Answer 1

将PitchPosition查询集传递给序列化程序时，可以使用Prefetch个对象来控制Pattern个对象的顺序。