How to make a field in Serializer both readable and writeable

Question

I am writing a Serializer for my model which will be accessed using GET, POST and PATCH endpoints. I have a property in my model which I am using as a source for a field. However, using source= in serializer field is making it ready-only.

If I remove the source="get_field1" from the

field1 = serializers.NullBooleanField(source="get_field1")

then I am able to update the data.

But I HAVE to use the source to get the right value of the field.

class MyModel(models.Model):
    field1 = NullBooleanField(default=None)

    @property
    get_field1(self):
       data = True
       # ...some logic
       return data

Now I have a serializer that I am using

    class MyModelSerializer(serializers.ModelSerializer):
        field1 = serializers.NullBooleanField(source="get_field1")
        class Meta:
             model = MyModel
             fields = ('field1')

Now in my API endpoint, I do this

    serializer = MyModelSerializer(my_model, data=request.data, partial=True)
    if serializer.is_valid():
        serializer.save() # <- throws error "can't set attribute"

Also, I would like to mention that the field in the serializer is referred by the property name and not by the field name.

Example: If I do

>> serializer.validated_data

>> 'OrderedDict(['get_field1'], True) # <- shouldn't this by field1 and not get_field1

Answer 1

Answer by @JPG is good, but I feel it's a hacky way.

I would override the to_representation method of the Serializer to achieve your purpose.

Here's what you can do

class MyModelSerializer(serializers.ModelSerializer):
        field1 = serializers.NullBooleanField() # get rid of source

        def to_representation(self, instance):
             data = super(MyModel, self).to_representation(instance)
             data.update({
                  'field1': instance.get_field1
             })
             return data       

        class Meta:
             model = MyModel
             fields = ('field1')

This way you are implicitly providing the source and your field becomes writeable. So every time you GET, POST, or PATCH you'll get the right value.