Django Rest Framework不会序列化SerializerMethodField

Question

我有2个型号:

from django.db import models

STATUSES = (
    ('f', 'Finished'),
)


class Battery(models.Model):
    energy = models.CharField(max_length=10)
    current = models.CharField(max_length=10)


class Charger(models.Model):
    status = models.CharField(max_length=1, choices=STATUSES)

我想创建序列化器,将这2个模型序列化在一起.我的serializers.py:

from rest_framework import serializers
from .models import Battery, Charger


class BatterySerializer(serializers.ModelSerializer):
    class Meta:
        model = Battery


class ChargerSerializer(serializers.ModelSerializer):
    status = serializers.SerializerMethodField()

    class Meta:
        model = Charger

    def get_status(self, obj):
        return obj.get_status_display()


class DeviceSerializer(serializers.Serializer):
    battery = BatterySerializer()
    charger = ChargerSerializer()
    some_field = serializers.CharField()

由于Charger模型在状态字段中有选择,因此我添加了SerializerMethodField以显示完整状态.然后我创建一个这样的视图:

class DeviceView(APIView):
    def get(self, request, format=None):
        battery = Battery.objects.get(id=1)
        charger = Charger.objects.get(id=1)
        battery_serializer = BatterySerializer(battery)
        charger_serializer = ChargerSerializer(charger)
        serializer = DeviceSerializer(data={
            'battery': battery_serializer.data,
            'charger': charger_serializer.data,
            'some_field': 'some_text'
        })
        if serializer.is_valid():
            return Response(serializer.validated_data)
        else:
            return Response(status = 500)

但是,当我调用此视图时,它返回带有空充电器字段的json:

{
    "battery": {
        "energy": "12",
        "current": "34"
    },
    "charger": {},
    "some_field": "some_text"
}

但是当我创建一个仅序列化Charger模型的视图时:

class ChargerView(APIView):
    def get(self, request, format=None):
        charger = Charger.objects.get(id=1)
        charger_serializer = ChargerSerializer(charger)
        return Response(charger_serializer.data)

它工作,它返回这个json:

{
    "id": 1,
    "status": "Finished"
}

为什么会这样？我在哪里弄错了？

Answer 1

查看以下文档Serializers:

1. instance当你有一个对象并且你必须序列化它时传递.(链接)
2. data当您已经有序列化数据并且想要反序列化它并从中创建实例时传递.(链接)
3. 既instance与data当你有一个实例,并要更新它传递.(链接)

看看你的情况,我认为你不需要选项2和3,因为你有battery和charger实例,你需要将它们序列化.您没有创建新实例,也没有必要验证它,因此data不需要传递它.

有两种方法可以做到这一点:

1.创建一个类,Device以便您可以创建它的实例,然后使用DeviceSerializer以下命令对其进行序列化:

class Device(object):

    def __init__(self, battery, charger, some_field):
        self.battery = battery
        self.charger = charger
        self.some_field  = some_field

class DeviceView(APIView):
    # then in the DeviceView you could create an instance and pass to the serializer
    def get(self, request, format=None):
        battery = Battery.objects.get(id=1)
        charger = Charger.objects.get(id=1)
        device = Device(battery=battery, charger=charger, some_field='some_text')
        serializer = DeviceSerializer(instance=device)
        return Response(serializer.data)

2.如果您不想创建新类,可以直接创建dict并将其作为实例传递:

class DeviceView(APIView):
    def get(self, request, format=None):
        battery = Battery.objects.get(id=1)
        charger = Charger.objects.get(id=1)
        # create a dict with required objects and pass it as instance of serializer
        device = {'battery': battery, 'charger': charger, 'some_field': 'some_text'}
        serializer = DeviceSerializer(instance=device)
        return Response(serializer.data)