如何在Django Rest Framework中使用GenericRelation？

Question

我想包括在DRF

该文档与GenericRelation backrefrence的模型表明，这应该是很容易（略高于：http://www.django-rest-framework.org/api-guide/relations/#manytomanyfields-with-a-through-model） - 但我失去了一些东西！

注意，反向通用密钥，使用GenericRelation 字段中表达，可以使用常规关系字段类型， 由于目标的关系中的类型总是已知的序列化。

欲了解更多信息，请参阅关于通用 关系的Django文档。

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') 

两个注释掉线是我在告诉DRF如何序列尝试voteable内Question
第一个给我

'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，很明显，我误解的东西，任何想法是什么？

Answer 1

嗯，我有一个有效的解决方案，但它不觉得自己是正确的解决方案....

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从VoteableSerializer
• 变化VoteableSerializer到ModelSerializer从HyperlinkedModelSerializer
• 删除添加VoteableRelatedField并从查询集中获取第一项（特别感觉不对）

我不会将此标记为已接受，希望有人能启发我如何应该完成！解决的办法，这似乎更适合GenericRelation

Answer 2

另类的想法...

• 让Voteable的抽象模型
• 阿尔特投票类（在这个问题上未显示）使用GenericForeignKey在任何点。

优点：
这将意味着票信息永远是对相关对象上，简化分类&查询，避免加入。

缺点：
投票将采取多一点空间

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') 

---

或许更优化，但少干。将有继承Voteable每种类型的对象的一个​​单独的“投票”类

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

定制相关的串行领域似乎不必要的doc有这个脚注Generi cRelation：

注意，反向通用密钥，使用GenericRelation 字段中表达，可以使用常规关系字段类型， 由于目标的关系中的类型总是已知的序列化。

以下申请。还请检查this DRF3扩展。

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

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