[英]Access different fields on 'ManyRelatedManager' using Django Rest Framework?
我正在嘗試訪問ManyToMany鏈接的直通表上的字段,以通過Django Rest框架序列化為JSON。
我的模型涉及多對多:
class Mage(models.Model):
arcana = models.ManyToManyField('ArcanumAbility', through='CharacterArcanumLink', related_name='mage_by_arcana')
class ArcanumAbility(models.Model):
class Arcana(AutoNumber):
FATE = ()
MIND = ()
SPIRIT = ()
DEATH = ()
FORCES = ()
TIME = ()
SPACE = ()
LIFE = ()
MATTER = ()
PRIME = ()
arcanum = EnumField(Arcana)
class Meta:
verbose_name_plural = "Arcana Abilities"
def __str__(self):
return self.arcanum.label
class CharacterArcanumLink(Trait):
PRIORITY_CHOICES = (
(0, 'Unassigned'), (1, 'Ruling'), (2, 'Common'), (3, 'Inferior')
)
priority = models.PositiveSmallIntegerField(
choices=PRIORITY_CHOICES, default=0)
mage = models.ForeignKey('Mage')
arcana = models.ForeignKey('ArcanumAbility')
class Meta:
unique_together = ('mage', 'arcana')
def __str__(self):
return self.arcana.arcanum.label
Trait
mixin提供current_value
要將上述關系序列化為我的JSON,我在我的序列化器上嘗試了這兩個模式:
class CharacterArcanumLinkSerializer(serializers.ModelSerializer):
class Meta:
model = CharacterArcanumLink
fields = ('current_value', 'arcana')
class MageSerializer(serializers.ModelSerializer):
arcana = CharacterArcanumLinkSerializer()
....
class Meta:
model = Mage
fields = (...., 'arcana', ....)
depth = 1
但這給了我這個錯誤:
AttributeError at /mages
'ManyRelatedManager' object has no attribute 'arcana'
哪個來自(最終):
C:\Python34\lib\site-packages\rest_framework\fields.py in get_attribute
if instance is None:
# Break out early if we get `None` at any point in a nested lookup.
return None
try:
if isinstance(instance, collections.Mapping):
instance = instance[attr]
else:
instance = getattr(instance, attr) ...
except ObjectDoesNotExist:
return None
if is_simple_callable(instance):
instance = instance()
return instance
▼ Local vars
Variable: Value
instance: <django.db.models.fields.related.create_many_related_manager.<locals>.ManyRelatedManager object at 0x0000000004E4D4A8>
attr: 'arcana'
attrs: ['arcana']
(問題:我需要從ManyRelatedManager到其字段的哪些技巧?)
而且我也嘗試過不指定一個特殊的序列化器,只是在我的字段中使用'arcana'
,然后從我的模型中取出它。 這導致了這個錯誤:
TypeError at /mages
<Arcana.FATE: 1> is not JSON serializable
其中1
來自ArcanumAbility上的PK而不是直通表上的值。 這里的問題是Mage類有一個指向'ArcanumAbility'
模型的M2M字段,所以DRF嘗試做的就是序列化它上面的Enum。
那么,如果我想要一個包含從Mage到ArcanumAbility的所有關系的JSON字典以及來自直通表的數據,我應該使用什么方法?
回應Mark R. ,我希望它看起來像這樣:
....
"arcanum": {
"Fate": 2,
"Spirit": 0,
"Mind": 3,
....
}
希望這是一個足夠清晰的樣本。
如上所述,如果將一個related_name =“linked_arcana”添加到CharacterArcanumLink類的mage字段中,您應該可以執行以下操作:
class MageSerializer(serializers.ModelSerializer):
arcana = serializers.SerializerMethodField()
def get_arcana(self, obj):
if obj:
return {str(x): x.current_value for x in obj.linked_arcana.all()}
我有這樣的工作:
arcana = serializers.SerializerMethodField()
def get_arcana(self, obj):
if obj:
return {str(link): link.current_value
for link in CharacterArcanumLink.objects.filter(mage=obj)}
這個答案深受啟發。
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