ValidationError与Django REST API和generic_relations用于通用外键可写访问

Question

我正在使用Django REST API和generic_relations模块来创建一种Django Comments的变体，它不是由模板驱动的，而是通过REST API函数。

Model类命名为Annotation，类似于:

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，有另一个模型，内容，它可以是几乎任何东西，所以我们说，它是一个简单的张贴应用程序:

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')

相同的序列化器如下:

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，问题在这一行:content_object = GenericRelatedField({BlogContent: serializers.HyperlinkedRelatedField (view_name = '注释:blogcontent-detail '),}, read_only = False)

如果通用关系被用作只读，通过设置read_only=True，那么REST API的可浏览性是好的，但是当我切换到False时，服务器抛出一个ValidationError

ValidationError at /en/annotation/
[u'Invalid model - model not available.']

仔细阅读日志和代码，似乎在rest_framework.renderers.py中get_raw_data_form(self, view, method, request)没有在调用obj = getattr(view, 'object', None)中找到对象。

这反过来，当field_to_native函数在generic_relations中作为serializer = self.determine_deserializer_for_data(value)求值时，导致没有作为value传入，因此，代码中断。

有其他人也遇到这样的错误和/或可以帮助我修复它吗?请帮助!

回溯如下:

/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

Answer 1

存储库上的这个问题也提到了相同的错误，但在不同的上下文中，提供的解决方案仍然适用于我，直到作者发布修复。

解决方法是在调用super方法后添加if value:子句。