Django Rest Framework 使用 filterset_fields 过滤 ViewSet 中计算的 SerializerMethodField()

Question

我有一个 SerializerMethodField 计算下一个执行日期，将小时数添加到上次执行时间

简化代码，有这个模型：

class Activity(BaseModel):
    name = models.CharField(max_length=250)
    last_execution = models.DateTimeField()

    def __str__(self):
        return self.name

    class Meta:
        ordering = ('name',)

为了在下一次执行时间发送到前端，我的Serializer中有这个SerializerMethodField()

class ActivitySerializer(serializers.ModelSerializer):
    next_execution = serializers.SerializerMethodField('get_next_execution')

    class Meta:
        model = Activity
        fields = ('id', 'name', 'last_execution', 'next_execution',)

    def get_next_execution(self, data):
        # last = ActivityExecute.objects.filter(activity_id=data.id).order_by('-executed_at').first()
        # time = data.periodicity_type.time_in_hour
        # if last:
        #     if data.equipment.hour_meter > -1:
        #         return last.executed_at + timedelta(hours=time - (data.equipment.hour_meter - last.hour_meter))
        #     return last.executed_at + timedelta(hours=time)
        # 
        # return data.equipment.created_at + timedelta(hours=time)
        return data.last_execution + timedelta(hours=24)

但是当我尝试像这样将计算字段添加到filterset_fields 时：

class ActivityViewSet(viewsets.ModelViewSet):
    permission_classes = (IsAuthenticated,)

    serializer_class = ActivitySerializer
    filter_backends = (filters.DjangoFilterBackend,)
    filterset_fields = {
        'id': ['exact'],
        'name': ['icontains', 'exact'],
        'last_execution': ['exact'],
        'next_execution': ['exact'],
    }

    def get_object(self):
        return super(ActivityViewSet, self).get_object()

    def get_queryset(self):
        return Activity.objects.all()

我收到了这个错误： 'Meta.fields' must not contain non-model field names: next_execution

有没有办法将SerializerMethodField() 添加到filterset_fields？使用方法get_queryset 将使我在该计算字段（已注释）中的所有逻辑都被复制。该字段工作正常，问题只是前端使用查询参数过滤值。

Answer 1

如果您可以为您的项目添加一个包，使用django-property-filter 会很容易

只需将您的序列化程序代码转换为如下属性：

class Activity(BaseModel):
    name = models.CharField(max_length=250)
    last_execution = models.DateTimeField()

    def __str__(self):
        return self.name

    class Meta:
        ordering = ('name',)

    @property
    def next_execution(self):
        # all your logic in comment can be pasted here
        return self.last_execution + timedelta(hours=24)  

从serializer 中删除您的SerializerMethodField() 和def get_next_execution，但将其保留在字段列表中，此属性也将作为字段列出

class ActivitySerializer(serializers.ModelSerializer):

    class Meta:
        model = Activity
        fields = ('id', 'name', 'last_execution', 'next_execution',)

现在，在视图中，从您的ViewSet 中删除filterset_fields，我们会将其添加到FilterSet 类中...

为您的ViewSet 创建一个FilterSet

from django_property_filter import PropertyFilterSet, PropertyDateFilter

class ActivityFilterSet(PropertyFilterSet):
    next_execution = PropertyDateFilter(field_name='next_execution', lookup_expr='exact') # this is the @property that will be filtered as a DateFilter, you can change the variable name, just keep the `field_name` right

    class Meta:
        model = Activity
        fields = { # here is the filterset_fields property
            'id': ['exact'],
            'name': ['icontains', 'exact'],
            'last_execution': ['exact'],
        }

然后，只需将此 FilterSet 添加到您的 ViewSet 中，奇迹就会发生

class ActivityViewSet(viewsets.ModelViewSet):
    permission_classes = (IsAuthenticated,)

    serializer_class = ActivitySerializer
    filter_backends = (filters.DjangoFilterBackend,)
    filterset_class = ActivityFilterSet

    def get_object(self):
        return super(ActivityViewSet, self).get_object()

    def get_queryset(self):
        return Activity.objects.all()

Answer 2

我真的不喜欢django-filter - 这是我更喜欢的一种方法，它让我们（几乎）可以通过几行代码从前端完全访问 django-orm：

class BaseViewSet(viewsets.ModelViewSet):

    def get_queryset(self):
        queryset = self.queryset
        custom_filter = self.request.query_params.get('filter')
        custom_exclude = self.request.query_params.get('exclude')
    
        if custom_filter: 
            custom_filter = json.loads(custom_filter)
            queryset = queryset.filter(**custom_filter)
        
        if custom_exclude: 
            custom_exclude = json.loads(custom_exclude)
            queryset = queryset.exclude(**custom_exclude)
        
        return queryset

现在我们可以像这样发送请求：

// django-like filter:
var filter = {
  last_execution : '2020-01-01 08:20:20'
}

$.ajax({
  url : 'api/activities/?filter=' + JSON.stringify(filter)
  type : 'GET',
  success : function(response){...},
  ...
});

基本上，您的网址现在看起来像：

https://mywebsite.com/api/activities/?filter={"last_execution":"2020-01-01 08:20:20"}

现在我们可以在 js 代码中为 last_execution_date 添加 24 小时来检索 activity（而不是在 python 端这样做）：

// can use libraries like moment.js etc:
var filter = {
  last_execution : '2020-01-02 08:20:20'
}

$.ajax({...});

就是这样！不再向每个视图集添加字段。