diff --git a/docs/api-guide/serializers.md b/docs/api-guide/serializers.md index 6b91aa764..4c3fb9d33 100644 --- a/docs/api-guide/serializers.md +++ b/docs/api-guide/serializers.md @@ -67,6 +67,21 @@ At this point we've translated the model instance into Python native datatypes. json # '{"email": "leila@example.com", "content": "foo bar", "created": "2012-08-22T16:20:09.822"}' +### Customizing field representation + +Sometimes when serializing objects, you may not want to represent everything exactly the way it is in your model. + +If you need to customize the serialized value of a particular field, you can do this by creating a `transform_` method. For example if you needed to render some markdown from a text field: + + description = serializers.TextField() + description_html = serializers.TextField(source='description', read_only=True) + + def transform_description_html(self, obj, value): + from django.contrib.markup.templatetags.markup import markdown + return markdown(value) + +These methods are essentially the reverse of `validate_` (see *Validation* below.) + ## Deserializing objects Deserialization is similar. First we parse a stream into Python native datatypes... diff --git a/rest_framework/serializers.py b/rest_framework/serializers.py index 8d2e0feb8..7bb0f3ee8 100644 --- a/rest_framework/serializers.py +++ b/rest_framework/serializers.py @@ -307,6 +307,9 @@ class BaseSerializer(WritableField): field.initialize(parent=self, field_name=field_name) key = self.get_field_key(field_name) value = field.field_to_native(obj, field_name) + method = getattr(self, 'transform_%s' % field_name, None) + if callable(method): + value = method(obj, value) ret[key] = value ret.fields[key] = field return ret diff --git a/rest_framework/tests/test_serializer.py b/rest_framework/tests/test_serializer.py index 8d246b010..8281bd905 100644 --- a/rest_framework/tests/test_serializer.py +++ b/rest_framework/tests/test_serializer.py @@ -1659,3 +1659,38 @@ class SerializerSupportsManyRelationships(TestCase): serializer = SimpleSlugSourceModelSerializer(data={'text': 'foo', 'targets': [1, 2]}) self.assertTrue(serializer.is_valid()) self.assertEqual(serializer.data, {'text': 'foo', 'targets': [1, 2]}) + + +class TransformMethodsSerializer(serializers.Serializer): + a = serializers.CharField() + b_renamed = serializers.CharField(source='b') + + def transform_a(self, obj, value): + return value.lower() + + def transform_b_renamed(self, obj, value): + if value is not None: + return 'and ' + value + + +class TestSerializerTransformMethods(TestCase): + def setUp(self): + self.s = TransformMethodsSerializer() + + def test_transform_methods(self): + self.assertEqual( + self.s.to_native({'a': 'GREEN EGGS', 'b': 'HAM'}), + { + 'a': 'green eggs', + 'b_renamed': 'and HAM', + } + ) + + def test_missing_fields(self): + self.assertEqual( + self.s.to_native({'a': 'GREEN EGGS'}), + { + 'a': 'green eggs', + 'b_renamed': None, + } + )