如何在Django Rest Framework中使用GenericRelation？

Question

我想包括在DRF

該文檔與GenericRelation backrefrence的模型表明，這應該是很容易（略高於：http://www.django-rest-framework.org/api-guide/relations/#manytomanyfields-with-a-through-model） - 但我失去了一些東西！

注意，反向通用密鑰，使用GenericRelation 字段中表達，可以使用常規關係字段類型， 由於目標的關係中的類型總是已知的序列化。

欲瞭解更多信息，請參閱關於通用 關係的Django文檔。

我的模型：

class Voteable(models.Model): 
    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE) 
    object_id = models.PositiveIntegerField() 
    content_object = GenericForeignKey('content_type', 'object_id') 

    direct_vote_count = models.IntegerField(default=0) 

class Question(models.Model): 
    user = models.ForeignKey(UserExtra, related_name='questions_asked') 
    voteable = GenericRelation(Voteable) 
    question = models.CharField(max_length=200) 

和我的串行：

class VoteableSerializer(serializers.HyperlinkedModelSerializer): 
    class Meta: 
     model = Voteable 
     fields = ('pk', 'id', 'url', 'direct_vote_count') 


class QuestionSerializer(serializers.HyperlinkedModelSerializer): 
    #voteable = VoteableSerializer(read_only=True, many=False) 
    #voteable = serializers.PrimaryKeyRelatedField(many=False, read_only=True) 

    class Meta: 
     depth = 1 
     model = Question 
     fields = ('url', 'question', 'user', 'voteable') 

兩個註釋掉線是我在告訴DRF如何序列嘗試voteable內Question
第一個給我

'GenericRelatedObjectManager' object has no attribute 'pk'

和第二

<django.contrib.contenttypes.fields.create_generic_related_manager.<locals>.GenericRelatedObjectManager object at 0x7f7f3756cf60> is not JSON serializable

因此，很明顯，我誤解的東西，任何想法是什麼？

Answer 1

嗯，我有一個有效的解決方案，但它不覺得自己是正確的解決方案....

class VoteableSerializer(serializers.ModelSerializer): 
    class Meta: 
     model = Voteable 
     fields = ('pk', 'direct_vote_count') 


class VoteableRelatedField(serializers.RelatedField): 
    def to_representation(self, value): 
     serializer = VoteableSerializer(value.get_queryset()[0]) 
     return serializer.data 

class QuestionSerializer(serializers.HyperlinkedModelSerializer): 
    #voteable = VoteableSerializer(read_only=True, many=False) 
    #voteable = serializers.PrimaryKeyRelatedField(many=False, read_only=True) 

    voteable = VoteableRelatedField(read_only=True) 

    class Meta: 
     depth = 1 
     model = Question 
     fields = ('url', 'question', 'user', 'voteable') 
     read_only_fields = ('voteable',) 

• url從VoteableSerializer
• 變化VoteableSerializer到ModelSerializer從HyperlinkedModelSerializer
• 刪除添加VoteableRelatedField並從查詢集中獲取第一項（特別感覺不對）

我不會將此標記爲已接受，希望有人能啓發我如何應該完成！解決的辦法，這似乎更適合GenericRelation

Answer 2

另類的想法...

• 讓Voteable的抽象模型
• 阿爾特投票類（在這個問題上未顯示）使用GenericForeignKey在任何點。

優點：
這將意味着票信息永遠是對相關對象上，簡化分類&查詢，避免加入。

缺點：
投票將採取多一點空間

class Voteable(models.Model): 
    votes = GenericRelation(Vote) 
    direct_vote_count = models.IntegerField(default=0) 

    class Meta: 
     abstract = True 

class Question(Voteable): 
    user = models.ForeignKey(UserExtra, related_name='questions_asked') 
    question = models.CharField(max_length=200) 

class Vote(models.Model): 
    user = models.ForeignKey(UserExtra, related_name='questions_asked') 
    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE) 
    object_id = models.PositiveIntegerField() 
    content_object = GenericForeignKey('content_type', 'object_id') 

---

或許更優化，但少幹。將有繼承Voteable每種類型的對象的一個​​單獨的「投票」類

class Voteable(models.Model): 
    direct_vote_count = models.IntegerField(default=0) 

    class Meta: 
     abstract = True 

class Question(Voteable): 
    user = models.ForeignKey(UserExtra, related_name='questions_asked') 
    question = models.CharField(max_length=200) 

class QuestionVote(models.Model):#This class also repeated for each item that can be voted on 
    user = models.ForeignKey(UserExtra, related_name='questions_asked') 
    parent = models.ForeignKey(Question, related_name='votes') 

Answer 3

定製相關的串行領域似乎不必要的doc有這個腳註Generi cRelation：

注意，反向通用密鑰，使用GenericRelation 字段中表達，可以使用常規關係字段類型， 由於目標的關係中的類型總是已知的序列化。

以下申請。還請檢查this DRF3擴展。

class QuestionSerializer(serializers.HyperlinkedModelSerializer): 
    voteable = VoteableSerializer(read_only=True) 

    class Meta: 
     model = Question 
     fields = ('url', 'question', 'user', 'voteable') 
     ...