NotImplemented stubs for Field, and DecimalField improvements

rest_framework/fields.py

@@ -229,13 +229,13 @@ class Field(object):
         """
         Transform the *incoming* primative data into a native value.
         """
-        return data
+        raise NotImplementedError('to_native() must be implemented.')
 
     def to_primative(self, value):
         """
         Transform the *outgoing* native value into primative data.
         """
-        return value
+        raise NotImplementedError('to_primative() must be implemented.')
 
     def fail(self, key, **kwargs):
         """
@@ -429,9 +429,10 @@ class DecimalField(Field):
         'max_whole_digits': _('Ensure that there are no more than {max_whole_digits} digits before the decimal point.')
     }
 
-    def __init__(self, max_value=None, min_value=None, max_digits=None, decimal_places=None, **kwargs):
-        self.max_value, self.min_value = max_value, min_value
-        self.max_digits, self.max_decimal_places = max_digits, decimal_places
+    def __init__(self, max_digits, decimal_places, coerce_to_string=True, max_value=None, min_value=None, **kwargs):
+        self.max_digits = max_digits
+        self.decimal_places = decimal_places
+        self.coerce_to_string = coerce_to_string
         super(DecimalField, self).__init__(**kwargs)
         if max_value is not None:
             self.validators.append(validators.MaxValueValidator(max_value))
@@ -478,12 +479,26 @@ class DecimalField(Field):
         if self.max_digits is not None and digits > self.max_digits:
             self.fail('max_digits', max_digits=self.max_digits)
         if self.decimal_places is not None and decimals > self.decimal_places:
-            self.fail('max_decimal_places', max_decimal_places=self.max_decimal_places)
+            self.fail('max_decimal_places', max_decimal_places=self.decimal_places)
         if self.max_digits is not None and self.decimal_places is not None and whole_digits > (self.max_digits - self.decimal_places):
             self.fail('max_whole_digits', max_while_digits=self.max_digits - self.decimal_places)
 
         return value
 
+    def to_primative(self, value):
+        if not self.coerce_to_string:
+            return value
+
+        if isinstance(value, decimal.Decimal):
+            context = decimal.getcontext().copy()
+            context.prec = self.max_digits
+            quantized = value.quantize(
+                decimal.Decimal('.1') ** self.decimal_places,
+                context=context
+            )
+            return '{0:f}'.format(quantized)
+        return '%.*f' % (self.max_decimal_places, value)
+
 
 # Date & time fields...
 

rest_framework/pagination.py

@@ -37,7 +37,7 @@ class PreviousPageField(serializers.Field):
         return replace_query_param(url, self.page_field, page)
 
 
-class DefaultObjectSerializer(serializers.Field):
+class DefaultObjectSerializer(serializers.ReadOnlyField):
     """
     If no object serializer is specified, then this serializer will be applied
     as the default.
@@ -79,6 +79,6 @@ class PaginationSerializer(BasePaginationSerializer):
     """
     A default implementation of a pagination serializer.
     """
-    count = serializers.Field(source='paginator.count')
+    count = serializers.ReadOnlyField(source='paginator.count')
     next = NextPageField(source='*')
     previous = PreviousPageField(source='*')

rest_framework/utils/encoders.py

@@ -43,7 +43,7 @@ class JSONEncoder(json.JSONEncoder):
         elif isinstance(o, datetime.timedelta):
             return str(o.total_seconds())
         elif isinstance(o, decimal.Decimal):
-            return str(o)
+            return float(o)
         elif isinstance(o, QuerySet):
             return list(o)
         elif hasattr(o, 'tolist'):

tests/test_filters.py

@@ -102,7 +102,7 @@ if django_filters:
 
 class CommonFilteringTestCase(TestCase):
     def _serialize_object(self, obj):
-        return {'id': obj.id, 'text': obj.text, 'decimal': obj.decimal, 'date': obj.date}
+        return {'id': obj.id, 'text': obj.text, 'decimal': str(obj.decimal), 'date': obj.date}
 
     def setUp(self):
         """
@@ -145,7 +145,7 @@ class IntegrationTestFiltering(CommonFilteringTestCase):
         request = factory.get('/', {'decimal': '%s' % search_decimal})
         response = view(request).render()
         self.assertEqual(response.status_code, status.HTTP_200_OK)
-        expected_data = [f for f in self.data if f['decimal'] == search_decimal]
+        expected_data = [f for f in self.data if Decimal(f['decimal']) == search_decimal]
         self.assertEqual(response.data, expected_data)
 
         # Tests that the date filter works.
@@ -168,7 +168,7 @@ class IntegrationTestFiltering(CommonFilteringTestCase):
         request = factory.get('/', {'decimal': '%s' % search_decimal})
         response = view(request).render()
         self.assertEqual(response.status_code, status.HTTP_200_OK)
-        expected_data = [f for f in self.data if f['decimal'] == search_decimal]
+        expected_data = [f for f in self.data if Decimal(f['decimal']) == search_decimal]
         self.assertEqual(response.data, expected_data)
 
     @unittest.skipUnless(django_filters, 'django-filter not installed')
@@ -201,7 +201,7 @@ class IntegrationTestFiltering(CommonFilteringTestCase):
         request = factory.get('/', {'decimal': '%s' % search_decimal})
         response = view(request).render()
         self.assertEqual(response.status_code, status.HTTP_200_OK)
-        expected_data = [f for f in self.data if f['decimal'] < search_decimal]
+        expected_data = [f for f in self.data if Decimal(f['decimal']) < search_decimal]
         self.assertEqual(response.data, expected_data)
 
         # Tests that the date filter set with 'gt' in the filter class works.
@@ -230,7 +230,7 @@ class IntegrationTestFiltering(CommonFilteringTestCase):
         response = view(request).render()
         self.assertEqual(response.status_code, status.HTTP_200_OK)
         expected_data = [f for f in self.data if f['date'] > search_date and
-                         f['decimal'] < search_decimal]
+                         Decimal(f['decimal']) < search_decimal]
         self.assertEqual(response.data, expected_data)
 
     @unittest.skipUnless(django_filters, 'django-filter not installed')

tests/test_pagination.py

@@ -135,7 +135,7 @@ class IntegrationTestPaginationAndFiltering(TestCase):
 
         self.objects = FilterableItem.objects
         self.data = [
-            {'id': obj.id, 'text': obj.text, 'decimal': obj.decimal, 'date': obj.date}
+            {'id': obj.id, 'text': obj.text, 'decimal': str(obj.decimal), 'date': obj.date}
             for obj in self.objects.all()
         ]
 
@@ -381,7 +381,7 @@ class TestMaxPaginateByParam(TestCase):
 
 # Tests for context in pagination serializers
 
-class CustomField(serializers.Field):
+class CustomField(serializers.ReadOnlyField):
     def to_native(self, value):
         if 'view' not in self.context:
             raise RuntimeError("context isn't getting passed into custom field")