將用戶特定字段添加到Django REST Framework序列化程序

Question

我想在序列化程序中添加一個字段，其中包含特定於發出當前請求的用戶的信息（我不想為此創建單獨的端點）。 這是我做的方式：

視圖集：

class ArticleViewSet(viewsets.ModelViewSet):
    queryset = Article.objects.all()
    serializer_class = ArticleSerializer
    filter_class = ArticleFilterSet

    def prefetch_likes(self, ids):
        self.current_user_likes = dict([(like.article_id, like.pk) for like in Like.objects.filter(user=self.request.user, article_id__in=ids)])

    def get_object(self, queryset=None):
        article = super(ArticleViewSet, self).get_object(queryset)
        self.prefetch_likes([article.pk])
        return article

    def paginate_queryset(self, queryset, page_size=None):
        page = super(ArticleViewSet, self).paginate_queryset(queryset, page_size)
        if page is None:
            return None

        ids = [article.pk for article in page.object_list]
        self.prefetch_likes(ids)

        return page

序列化器：

class ArticleSerializer(serializers.ModelSerializer):
    class Meta:
        model = Article

    def to_native(self, obj):
        ret = super(ArticleSerializer, self).to_native(obj)

        if obj:
            view = self.context['view']
            ret['has_liked'] = False
            if hasattr(view, 'current_user_liked'):
                ret['has_liked'] = obj.pk in view.current_user_liked

        return ret

是否有更好的地方注入喜歡的文章的預取，或更好的方式來做到這一般？

Answer 1

你可以用SerializerMethodField做到這一點

示例：

class PostSerializer(serializers.ModelSerializer):
    fav = serializers.SerializerMethodField('likedByUser')

    def likedByUser(self, obj):
        request = self.context.get('request', None)
        if request is not None:
            try:
                liked=Favorite.objects.filter(user=request.user, post=obj.id).count()
                return liked == 1
            except Favorite.DoesNotExist:
                return False
        return "error"

    class Meta:
        model = Post

然后你應該從這個視圖調用序列化器：

class PostView(APIVIEW):
     def get(self,request):
         serializers = PostSerializer(PostObjects,context={'request':request})

Answer 2

我傾向於嘗試在Like模型對象上盡可能多地放置這個，然后在自定義序列化器字段中將其余部分打包。

在序列化程序字段中，您可以通過它們從父序列化程序繼承的context參數來訪問request 。

所以你可能會這樣做：

class LikedByUserField(Field):
    def to_native(self, article):
        request = self.context.get('request', None)
        return Like.user_likes_article(request.user, article)

然后user_likes_article類方法可以封裝您的預取（和緩存）邏輯。

我希望有所幫助。

Answer 3

根據Django文檔 - SerializerMethodField ，我不得不稍微改變rapid2share的代碼。

class ResourceSerializer(serializers.ModelSerializer):
    liked_by_user = serializers.SerializerMethodField()

    def get_liked_by_user(self, obj : Resource):
        request = self.context.get('request')
        return request is not None and obj.likes.filter(user=request.user).exists()