python - Django Rest Framework - How to add custom field in ModelSerializer

Question

I created a ModelSerializer and want to add a custom field which is not part of my model.

I found a description to add extra fields here and I tried the following:

customField = CharField(source='my_field')

When I add this field and call my validate() function then this field is not part of the attr dict. attr contains all model fields specified except the extra fields. So I cannot access this field in my overwritten validation, can I?

When I add this field to the field list like this:

class Meta:
    model = Account
    fields = ('myfield1', 'myfield2', 'customField')

then I get an error because customField is not part of my model - what is correct because I want to add it just for this serializer.

Is there any way to add a custom field?

Answer 1

In fact there a solution without touching at all the model. You can use SerializerMethodField which allow you to plug any method to your serializer.

class FooSerializer(ModelSerializer):
    foo = serializers.SerializerMethodField()

    def get_foo(self, obj):
        return "Foo id: %i" % obj.pk