Django Rest Framework UpdateAPIView is saying a field is required but the field is there

I have this model that represents an Ad:

class BigAd(models.Model):
    DA = 'DA'
    WE = 'WE'
    MO = 'MO'
    INTERVAL = [
        (DA, 'Day'),
        (WE, 'Week'),
        (MO, 'Month'),
    ]
    IM = 'IM'
    VI = 'VI'
    TYPES = [
        (IM, 'Image'),
        (VI, 'Video'),
    ]
    title = models.CharField(max_length=50, default=None)
    campaign = models.ForeignKey(Campaign, on_delete=models.CASCADE)
    audience = models.ForeignKey(AdAudience, on_delete=models.CASCADE, default=None)
    active = models.BooleanField(default=False)
    body = models.TextField(max_length=255, null=True, blank=True)
    ad_image = models.FileField(upload_to=bigad_directory_path, null=True, blank=True)
    ad_type = models.CharField(max_length=2, choices=TYPES, default=IM)
    big_image = models.FileField(upload_to=bigad_directory_path, null=True, blank=True)
    video = models.FileField(upload_to=bigad_video_path, null=True, blank=True)
    link = models.URLField(max_length=256, null=True, blank=True)
    budget_interval = models.CharField(max_length=2, choices=INTERVAL, default=DA)
    budget = models.DecimalField(max_digits=30, decimal_places=0, default=200)
    lowest_bid = models.DecimalField(max_digits=20, decimal_places=2)
    highest_bid = models.DecimalField(max_digits=20, decimal_places=2)
    includes_products = models.BooleanField(default=False)
    product_list = ArrayField(models.IntegerField(), null=True, blank=True)
    user = models.ForeignKey(User, on_delete=models.CASCADE, default=None)


    created_at = models.DateTimeField(auto_now_add=True, verbose_name="created at")
    updated_at = models.DateTimeField(auto_now=True, verbose_name="updated at")

    class Meta:
        verbose_name = "big ad"
        verbose_name_plural = "big ads"
        db_table = "big_ads"
        ordering = ["created_at"]

    def __str__(self):
            return self.title

    def get_absolute_url(self):
        return self.slug    

and this serializer for serializing the data:

class BigAdSerializer(serializers.ModelSerializer):
    campaign = ShortCampaignSerializer()
    class Meta:
        model = BigAd
        fields = [
            "id",
            "title",
            "campaign",
            "audience",
            "ad_image",
            "ad_type",
            "big_image",
            "active",
            "body",
            "video",
            "link",
            "budget_interval",
            "budget",
            "lowest_bid",
            "highest_bid",
            "user",
            "includes_products",
            "product_list",
            "active",
            "created_at",
            "updated_at",
        ]

and this view for processing the data:

class UpdateBigAd(generics.UpdateAPIView):
    permission_classes = [IsAuthenticated]
    serializer_class = AdSerializer
    def get_queryset(self):
        id = self.kwargs["pk"]
        return BigAd.objects.all().filter(id=id)

I am trying to update the ad model but I get an error saying campaign is required but the data is there and campaign has a value. Here is the data in the backend received:

(Pdb) print(request.data)
<QueryDict: {'active': ['on'], 'title': ['First Big AD'], 'campaign': ['20'], 'audience': ['10'], 'body': ['This is the first bog ad'], 'ad_image': [''], 'big_image': [''], 'link': ['https://post.com'], 'budget_interval': ['DA'], 'budget': ['200'], 'lowest_bid': ['10.00'], 'highest_bid': ['20']}>

I thought it could be that because campaign value is a string but then it would give me the same error for 'audience' which it doesn't. It also cannot be that it requires and object because then again it would give me the same error for audience.

Why then am I getting this error please?

As you defined campaign = ShortCampaignSerializer() your BigAdSerializer expects an object not an ID. Have a look to DRF documentation regarding nested serializers.

I suggest that you use two differents serializers for read and write operations :

class BigAdWriteSerializer(serializers.ModelSerializer):
   ... 

class BigAdReadSerializer(BigAdWriteSerializer):
    campaign = ShortCampaignSerializer()

You then need to override you update view method to use BigAdWriteSerializer to write data and then use BigAdReadSerializer to return data.