DRF Nested Serializer 字段未出现

Question

I'm trying to retrieve some data from two related models however i am unable (or would like to avoid to be more precise) to change the models. The problem is that the nested serializer doesn't return the data of the first model.

I have the following serializers

class NameSerializer(serializers.ModelSerializer):

    class Meta:
        model = Microcontrollers
        fields = ['name']


class DataCUTSerializer(QueryFieldsMixin, serializers.ModelSerializer):
    stationName = NameSerializer(read_only=True)
    
    class Meta:
        model = MeasurementsBasic
        fields = ['stationName', 'temp', 'hum']

    def to_representation(self, instance):
        representation = super().to_representation(instance)
        return {'timestamp': instance.time_taken,
                **representation}

        return representation

These serializers use the following models

class MeasurementsBasic(models.Model):
    microcontroller = models.OneToOneField('Microcontrollers', related_name='measurements_basic', primary_key=True, on_delete=models.CASCADE)
    time_taken = models.DateTimeField()
    time_received = models.DateTimeField(blank=True, null=True)
    frame = models.IntegerField(blank=True, null=True)
    temp = models.FloatField(blank=True, null=True)
    hum = models.FloatField(blank=True, null=True)
    pres = models.FloatField(blank=True, null=True)
    co = models.FloatField(blank=True, null=True)
    no2 = models.FloatField(blank=True, null=True)
    o3 = models.FloatField(blank=True, null=True)
    so2 = models.FloatField(blank=True, null=True)
    latitude = models.DecimalField(max_digits=9, decimal_places=6, blank=True, null=True)
    longitude = models.DecimalField(max_digits=9, decimal_places=6, blank=True, null=True)
    altitude = models.DecimalField(max_digits=9, decimal_places=6, blank=True, null=True)
    name = models.CharField(max_length=30, blank=True, null=True)

    class Meta:
        managed = True
        db_table = 'measurements_basic'
        unique_together = (('microcontroller', 'time_taken'),)

class Microcontrollers(models.Model):
    name = models.CharField(max_length=25)
    serial_number = models.CharField(max_length=20, blank=True, null=True)
    type = models.CharField(max_length=15, blank=True, null=True)
    software = models.CharField(max_length=20, blank=True, null=True)
    version = models.CharField(max_length=5, blank=True, null=True)
    date_installed = models.DateField(blank=True, null=True)
    date_battery_last_replaced = models.DateField(blank=True, null=True)
    source = models.CharField(max_length=10, blank=True, null=True)
    friendly_name = models.CharField(max_length=45, blank=True, null=True)
    private = models.IntegerField()
    datetime_updated = models.DateTimeField(db_column='DateTime_Updated')  # Field name made lowercase.

    class Meta:
        managed = True
        db_table = 'microcontrollers'
        verbose_name_plural = "Microcontrollers"

    def __str__(self):
        return self.friendly_name

Lastly my view

class TestData(generics.ListAPIView):
    serializer = DataCUTSerializer
            
    def get_queryset(self):
        final = []      
        allNames = ['SE1','SE3']
        for i in range(len(allNames)):
            measurements = MeasurementsBasic.objects.select_related('microcontroller').filter(microcontroller__name=allNames[i]).order_by('-time_taken')[:entries]
            final = list(chain(final, measurements))

        return final

    def list(self, request, *args, **kwargs):
        res = super(TestData, self).list(request, *args, **kwargs)
        res.data = {"stations": res.data}
        return res

My expected outcome is to get a json with timestamp, name, temp and hum. However i do not actually receive the name and get this instead.

{
    "stations": [
        {
            "timestamp": "2022-03-07T14:51:53",
            "temp": 16.18,
            "hum": 62.596
        },
        {
            "timestamp": "2022-03-07T14:42:48",
            "temp": 16.1,
            "hum": 62.856
        },
        {
            "timestamp": "2022-03-07T14:52:49",
            "temp": 18.43,
            "hum": 62.72
        },
        {
            "timestamp": "2022-03-07T14:43:43",
            "temp": 18.239,
            "hum": 62.134
        }
    ]
}

I checked the response and the data received is correct. Any help would be appreciated.

Answer 1

i think the problem is that you never passed data through serializer, try something like this:

views.py

from rest_framework.response import Response
from rest_framework import status

class TestData(generics.ListAPIView):
    serializer = DataCUTSerializer
            
    def get_queryset(self):
        allNames = ['SE1','SE3']
        # use list comprehension to better performance
        final = [
           chain(final, MeasurementsBasic.objects.select_related('microcontroller').filter(microcontroller__name=allNames[i]).order_by('-time_taken')[:entries]) for i in range(len(allNames))
        ]      
        return final

    def list(self, request, *args, **kwargs):
        serializer = DataCUTSerializer(self.get_queryset(), many=True)
        return Response({"stations": serializer.data}, status=status.HTTP_200_OK)