Django REST API 中使用 generic_relations 的 ValidationError 及可写外键访问问题
我正在使用Django REST API，并且结合generic_relations模块，创建一种类似于Django评论的功能，但不是通过模板，而是通过REST API的功能来实现。
我有一个模型类叫做Annotation，结构大致如下：
class Annotation(BaseCommentAbstractModel):
paragraph_id = models.PositiveIntegerField(null=False)
body = models.TextField()
'''
Annotations can be written only by logged in users. It is to prevent hit and run comments by people under anonymity.
'''
user = models.ForeignKey(DjangoUser, null=False, verbose_name=_('user'), related_name = "annotations")
现在，还有另一个模型，用于内容，这个内容可以是任何东西。比如说，它是一个简单的帖子应用：
class BlogContent(models.Model):
created = models.DateTimeField(auto_now_add=True)
title = models.CharField(max_length=100, blank=True, default='')
body = models.TextField()
...
annotation = GenericRelation(Annotation, content_type_field='content_type', object_id_field='object_pk')
对应的序列化器看起来是这样的：
from generic_relations.relations import GenericRelatedField
class BlogContentSerializer(serializers.ModelSerializer):
author_id = serializers.Field(source='author_id.username')
annotation = serializers.RelatedField(many=True)
class Meta:
model = BlogContent
fields = ('title','created','author_id',
'data','published_flag', 'url_path','slug','annotation')
class AnnotationSerializer(serializers.ModelSerializer):
user = serializers.Field(source='user.username')
content_object = GenericRelatedField({
BlogContent: serializers.HyperlinkedRelatedField(view_name='annotation:blogcontent-detail'),
}, read_only=False)
class Meta:
model = Annotation
fields = ('paragraph_id', 'body', 'user', 'content_object')
class UserSerializer(serializers.ModelSerializer):
blogcontent= serializers.PrimaryKeyRelatedField(many=True)
annotations = serializers.PrimaryKeyRelatedField(many=True)
class Meta:
model = User
fields = ('username', 'id', 'blogcontent', 'annotations')
现在，问题出在这一行： content_object = GenericRelatedField({ BlogContent: serializers.HyperlinkedRelatedField(view_name='annotation:blogcontent-detail'), }, read_only=False)
如果将通用关系设置为只读，也就是设置read_only=True，那么REST API的浏览功能是正常的。但一旦我把它改成False，服务器就会返回一个验证错误（ValidationError）。
ValidationError at /en/annotation/
[u'Invalid model - model not available.']
查看日志和代码后，似乎在rest_framework.renderers.py中的get_raw_data_form(self, view, method, request)方法里，调用obj = getattr(view, 'object', None)时找不到对象。
这又导致在评估field_to_native函数时，serializer = self.determine_deserializer_for_data(value)在generic_relations中，传入的value为空，因此代码就出错了。
有没有其他人遇到过这样的错误，或者能帮我解决这个问题吗？请帮帮我！
错误追踪信息如下：
/home/craft/pirateenv/lib/python2.7/site-packages/django/core/handlers/base.py in get_response
response = response.render() ...
▶ Local vars
/home/craft/pirateenv/lib/python2.7/site-packages/django/template/response.py in render
self.content = self.rendered_content ...
▶ Local vars
/home/craft/pirateenv/lib/python2.7/site-packages/rest_framework/response.py in rendered_content
ret = renderer.render(self.data, media_type, context) ...
▶ Local vars
/home/craft/pirateenv/lib/python2.7/site-packages/rest_framework/renderers.py in render
context = self.get_context(data, accepted_media_type, renderer_context) ...
▶ Local vars
/home/craft/pirateenv/lib/python2.7/site-packages/rest_framework/renderers.py in get_context
raw_data_post_form = self.get_raw_data_form(view, 'POST', request) ...
▶ Local vars
/home/craft/pirateenv/lib/python2.7/site-packages/rest_framework/renderers.py in get_raw_data_form
content = renderer.render(serializer.data, accepted, context) ...
▶ Local vars
/home/craft/pirateenv/lib/python2.7/site-packages/rest_framework/serializers.py in data
self._data = self.to_native(obj) ...
▶ Local vars
/home/craft/pirateenv/lib/python2.7/site-packages/rest_framework/serializers.py in to_native
value = field.field_to_native(obj, field_name) ...
▶ Local vars
/home/craft/pirateenv/lib/python2.7/site-packages/generic_relations/relations.py in field_to_native
serializer = self.determine_deserializer_for_data(value) ...
▶ Local vars
/home/craft/pirateenv/lib/python2.7/site-packages/generic_relations/relations.py in determine_deserializer_for_data
raise ValidationError(self.error_messages['no_model_match']) ...
▶ Local vars