How to update with SerializerMethodField in Django Rest Framework

Question

I have a field in my ModelSerializer which I've set as SerializerMethodField to modify the get behaviour for the field. I could update the data before, now I can't. How can I solve this?

Initially, without using SerializerMethodField, I got data like this:

    {
        ...
        "members": [2,3],
        ...
    }

but I added SerializerMethodField to modify the data, then update stopped working.

models.py

# Create your models here.
class Company(models.Model):
    members = ArrayField(models.IntegerField(blank=True), blank=True)
...

serializers.py

class AccountSerializer(serializers.ModelSerializer):
    user=serializers.StringRelatedField(read_only=False)
    class Meta:
        model=Account
        fields='__all__'

class UserSerializer(serializers.ModelSerializer):
    class Meta:
        model = User
        fields = '__all__'

class CompanySerializer(serializers.ModelSerializer):
    user = UserSerializer(read_only=False)
    members = serializers.SerializerMethodField()
    class Meta:
        model = Company
        fields = '__all__' #('id', 'name', 'description', 'date_created', 'user', 'status', 'theme', 'members')

    def get_members(self, obj):
        accounts = Account.objects.filter(id__in=obj.members)
        return AccountSerializer(accounts, many=True).data
...

Answer 1

1. You need to use different serializers for update and create. This serializer works for get only.

2. Or, you can create a custom field. Django Rest Framework How to update SerializerMethodField

3. Or, there can be other simpler hooks. If 'create' and 'update' worked as you wanted before modifiying members, then you can do as follow to get everything to default for create and update requests.

• Instead of using SerializerMethodField, override serializer representation.

class CompanySerializer(serializers.ModelSerializer):
    user = UserSerializer(read_only=False)

    class Meta:
        model = Company
        fields = ('id', 'name', 'description', 'date_created', 'user', 'status', 'theme', 'members', 'members_data')

    def to_representation(self, obj)
        ret = super().to_representation(obj)
        ret["members"] = AccountSerializer(accounts, many=True).data
        return ret

• Override the __init__ method . .

class CompanySerializer(serializers.ModelSerializer):
    user = UserSerializer(read_only=False)

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        try:
            if self.context['request'].method in ['GET']:
                self.fields['members'] = SerializerMethodField()
        except KeyError:
            pass

    class Meta:
        model = Company
        fields = '__all__' #('id', 'name', 'description', 'date_created', 'user', 'status', 'theme', 'members')

    def get_members(self, obj):
        accounts = Account.objects.filter(id__in=obj.members)
        return AccountSerializer(accounts, many=True).data
...

• Or, you can create different field for getting members.

class CompanySerializer(serializers.ModelSerializer):
    user = UserSerializer(read_only=False)
    members_data = SerializerMethodField()

    class Meta:
        model = Company
        fields = ('id', 'name', 'description', 'date_created', 'user', 'status', 'theme', 'members', 'members_data')

    def get_members_data(self, obj):
        accounts = Account.objects.filter(id__in=obj.members)
        return AccountSerializer(accounts, many=True).data
...