我正在尝试学习如何在Django-Rest-Framework中使用GenericRelations。我找到了serializer relations的文档页面并遵循了代码。我创建了模型:
class TaggedItem(models.Model):
"""
Tags arbitary model instance using a generic relation.
"""
tag_name = models.SlugField()
content_type = models.ForeignKey(ContentType)
object_id = models.PositiveIntegerField()
tagged_object = GenericForeignKey('content_type', 'object_id')
def __unicode__(self):
return self.tag_name
class Bookmark(models.Model):
"""
A bookmark consists of a URL, and 0 or more descriptive tags.
"""
link_url = models.URLField()
tags = GenericRelation(TaggedItem)
class Note(models.Model):
"""
A note consists of some texts, and 0 or more descriptive tags
"""
text = models.CharField(max_length=1000)
tags = GenericRelation(TaggedItem)
我创建了序列化器:
class BookmarkSerializer(serializers.ModelSerializer):
class Meta:
model = Bookmark
fields = ('url', 'link_url', )
class NoteSerializer(serializers.ModelSerializer):
class Meta:
model = Note
fields = ('url', 'text', )
class TaggedObjectRelatedField(serializers.RelatedField):
"""
A custom field to use for the 'tagged_object' generic relationship
"""
def to_representation(self, value):
"""
Serialize tagged objects to their respective serializer formats
:param value:
:return:
serializer.data
"""
if isinstance(value, Bookmark):
return 'Bookmark: ' + value.url
elif isinstance(value, Note):
return 'Note: ' + value.text
raise Exception('Unexpected type of tagged object')
class TaggedItemSerializer(serializers.ModelSerializer):
tagged_object = TaggedObjectRelatedField()
class Meta:
model = TaggedItem
fields = ('url', 'id', 'tag_name', 'tagged_object')
现在TaggedItemSerializer里面TaggedObjectRelatedField()的输入应该是什么?目前我收到错误
File "/home/aswin/Documents/WebProjects/drf_practice/uni_auth//loginpage/login/serializers.py", line 76, in TaggedItemSerializer
tagged_object = TaggedObjectRelatedField()
File "/home/aswin/Documents/WebProjects/drf_practice/uni_auth/lib/python3.5/site-packages/rest_framework/relations.py", line 80, in __init__
'Relational field must provide a `queryset` argument, '
AssertionError: Relational field must provide a `queryset` argument, override `get_queryset`, or set read_only=`True`.
我尝试将参数作为read_only = True给出,但它也引发了同样的错误。只是为了说明我的确做了什么:
class TaggedItemSerializer(serializers.ModelSerializer):
tagged_object = TaggedObjectRelatedField(read_only=True)
请在这件事上给予我帮助
我在文章中没有看到关于序列化TaggedItem的任何内容,为什么要序列化TaggedItem?
这是我的序列化程序类:
from models import Bookmark, Note, TaggedItem
from rest_framework import serializers
class TaggedObjectRelatedField(serializers.RelatedField):
def to_representation(self, value):
if isinstance(value, Bookmark):
serializer = BookMarkSerializer(value)
elif isinstance(value, Note):
serializer = NoteSerializer(value)
else:
raise Exception('Unexpected type of tagged object')
return serializer.data
class BookMarkSerializer(serializers.HyperlinkedModelSerializer):
tags = TaggedObjectRelatedField(many=True, queryset=TaggedItem.objects.all())
class Meta:
model = Bookmark
fields = ('pk', 'url', 'tags')
class NoteSerializer(serializers.HyperlinkedModelSerializer):
tags = TaggedObjectRelatedField(many=True, queryset=TaggedItem.objects.all())
class Meta:
model = Note
fields = ('pk', 'text', 'tags')
派对有点晚了,但我想如果你想为TaggedItem
创建一个序列化器,你可以结帐rest-framework-generic-relations。所以根据他们的文档,你可以创建类似的东西:
from generic_relations.relations import GenericRelatedField
class TagSerializer(serializers.ModelSerializer):
"""
A `TaggedItem` serializer with a `GenericRelatedField` mapping all possible
models to their respective serializers.
"""
tagged_object = GenericRelatedField({
Bookmark: BookmarkSerializer(),
Note: NoteSerializer()
})
class Meta:
model = TaggedItem
fields = ('tag_name', 'tagged_object')
或类似的东西:
class TagSerializer(serializers.ModelSerializer):
"""
A `Tag` serializer with a `GenericRelatedField` mapping all possible
models to properly set up `HyperlinkedRelatedField`s.
"""
tagged_object = GenericRelatedField({
Bookmark: serializers.HyperlinkedRelatedField(
queryset = Bookmark.objects.all(),
view_name='bookmark-detail',
),
Note: serializers.HyperlinkedRelatedField(
queryset = Note.objects.all(),
view_name='note-detail',
),
})
class Meta:
model = TaggedItem
fields = ('tag_name', 'tagged_object')